From ff4b471c9d73f110395c66eab4837c3794e71755 Mon Sep 17 00:00:00 2001 From: clintaire Date: Tue, 24 Jun 2025 20:00:50 +0000 Subject: [PATCH 1/2] Update directory --- DIRECTORY.md | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/DIRECTORY.md b/DIRECTORY.md index 5cc12315d10b..a41daf9a2934 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -595,6 +595,7 @@ * [BinarySearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/BinarySearch.java) * [BinarySearch2dArray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/BinarySearch2dArray.java) * [BM25InvertedIndex](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/BM25InvertedIndex.java) + * [BoyerMoore](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/BoyerMoore.java) * [BreadthFirstSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/BreadthFirstSearch.java) * [DepthFirstSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/DepthFirstSearch.java) * [ExponentalSearch](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/ExponentalSearch.java) @@ -629,7 +630,6 @@ * [MaxSumKSizeSubarray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/slidingwindow/MaxSumKSizeSubarray.java) * [MinSumKSizeSubarray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/slidingwindow/MinSumKSizeSubarray.java) * [ShortestCoprimeSegment](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/slidingwindow/ShortestCoprimeSegment.java) - * sorts * [AdaptiveMergeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/AdaptiveMergeSort.java) * [BeadSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/BeadSort.java) @@ -709,7 +709,6 @@ * [Alphabetical](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Alphabetical.java) * [Anagrams](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/Anagrams.java) * [CharactersSame](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/CharactersSame.java) - * [CheckAnagrams](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/CheckAnagrams.java) * [CheckVowels](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/CheckVowels.java) * [CountChar](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/CountChar.java) * [CountWords](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/strings/CountWords.java) @@ -1037,9 +1036,8 @@ * [MidpointEllipseTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/MidpointEllipseTest.java) * graph * [ConstrainedShortestPathTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/graph/ConstrainedShortestPathTest.java) - * [StronglyConnectedComponentOptimizedTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/graph/ + * [StronglyConnectedComponentOptimizedTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/graph/StronglyConnectedComponentOptimizedTest.java) * [TravelingSalesmanTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/graph/TravelingSalesmanTest.java) -StronglyConnectedComponentOptimizedTest.java) * greedyalgorithms * [ActivitySelectionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/greedyalgorithms/ActivitySelectionTest.java) * [BandwidthAllocationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/greedyalgorithms/BandwidthAllocationTest.java) @@ -1222,7 +1220,7 @@ StronglyConnectedComponentOptimizedTest.java) * [SudokuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/puzzlesandgames/SudokuTest.java) * [TowerOfHanoiTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/puzzlesandgames/TowerOfHanoiTest.java) * [WordBoggleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/puzzlesandgames/WordBoggleTest.java) - * randomize + * randomized * [KargerMinCutTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/randomized/KargerMinCutTest.java) * [MonteCarloIntegrationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/randomized/MonteCarloIntegrationTest.java) * [RandomizedQuickSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/randomized/RandomizedQuickSortTest.java) @@ -1260,6 +1258,7 @@ StronglyConnectedComponentOptimizedTest.java) * [BinarySearch2dArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/BinarySearch2dArrayTest.java) * [BinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/BinarySearchTest.java) * [BM25InvertedIndexTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/BM25InvertedIndexTest.java) + * [BoyerMooreTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/BoyerMooreTest.java) * [BreadthFirstSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/BreadthFirstSearchTest.java) * [DepthFirstSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/DepthFirstSearchTest.java) * [ExponentialSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/ExponentialSearchTest.java) @@ -1371,9 +1370,7 @@ StronglyConnectedComponentOptimizedTest.java) * [AhoCorasickTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AhoCorasickTest.java) * [AlphabeticalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java) * [AnagramsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/AnagramsTest.java) - * [CharacterSameTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CharacterSameTest.java) * [CharactersSameTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CharactersSameTest.java) - * [CheckAnagramsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CheckAnagramsTest.java) * [CheckVowelsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CheckVowelsTest.java) * [CountCharTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CountCharTest.java) * [CountWordsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/strings/CountWordsTest.java) From 20e6f4ef7c7605bfb1198b6e0d8bb4dffbffaba4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Clint=20Air=C3=A9?= <111376518+clintaire@users.noreply.github.com> Date: Fri, 11 Jul 2025 12:24:00 -0700 Subject: [PATCH 2/2] Add cache implementations and randomized algorithms --- .github/workflows/update-directorymd.yml | 42 ++ .../datastructures/caches/FIFOCache.java | 549 ++++++++++++++++++ .../datastructures/caches/RRCache.java | 505 ++++++++++++++++ .../randomized/RandomizedClosestPair.java | 113 ++++ ...mizedMatrixMultiplicationVerification.java | 64 ++ .../datastructures/caches/FIFOCacheTest.java | 330 +++++++++++ .../datastructures/caches/RRCacheTest.java | 222 +++++++ .../randomized/RandomizedClosestPairTest.java | 30 + ...dMatrixMultiplicationVerificationTest.java | 41 ++ 9 files changed, 1896 insertions(+) create mode 100644 .github/workflows/update-directorymd.yml create mode 100644 src/main/java/com/thealgorithms/datastructures/caches/FIFOCache.java create mode 100644 src/main/java/com/thealgorithms/datastructures/caches/RRCache.java create mode 100644 src/main/java/com/thealgorithms/randomized/RandomizedClosestPair.java create mode 100644 src/main/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerification.java create mode 100644 src/test/java/com/thealgorithms/datastructures/caches/FIFOCacheTest.java create mode 100644 src/test/java/com/thealgorithms/datastructures/caches/RRCacheTest.java create mode 100644 src/test/java/com/thealgorithms/randomized/RandomizedClosestPairTest.java create mode 100644 src/test/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerificationTest.java diff --git a/.github/workflows/update-directorymd.yml b/.github/workflows/update-directorymd.yml new file mode 100644 index 000000000000..53ad221e7742 --- /dev/null +++ b/.github/workflows/update-directorymd.yml @@ -0,0 +1,42 @@ +name: Generate Directory Markdown + +on: + push: + branches: [master] + workflow_dispatch: + +permissions: + contents: write + pull-requests: write + +jobs: + generate-directory: + runs-on: ubuntu-latest + steps: + - name: Checkout Repository + uses: actions/checkout@v4 + + - name: Run Directory Tree Generator + uses: DenizAltunkapan/directory-tree-generator@v2 + with: + path: src + extensions: .java + show-extensions: false + + - name: Commit changes + run: | + git config --global user.name "$GITHUB_ACTOR" + git config --global user.email "$GITHUB_ACTOR@users.noreply.github.com" + git add DIRECTORY.md + git diff --cached --quiet || git commit -m "Update DIRECTORY.md" + + - name: Create Pull Request + uses: peter-evans/create-pull-request@v7 + with: + token: ${{ secrets.REPO_SCOPED_TOKEN }} + branch: update-directory + base: master + title: "Update DIRECTORY.md" + body: "Automatically generated update of the directory tree." + commit-message: "Update DIRECTORY.md" + draft: false diff --git a/src/main/java/com/thealgorithms/datastructures/caches/FIFOCache.java b/src/main/java/com/thealgorithms/datastructures/caches/FIFOCache.java new file mode 100644 index 000000000000..fa048434a187 --- /dev/null +++ b/src/main/java/com/thealgorithms/datastructures/caches/FIFOCache.java @@ -0,0 +1,549 @@ +package com.thealgorithms.datastructures.caches; + +import java.util.Iterator; +import java.util.LinkedHashMap; +import java.util.LinkedHashSet; +import java.util.Map; +import java.util.Set; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.locks.Lock; +import java.util.concurrent.locks.ReentrantLock; +import java.util.function.BiConsumer; + +/** + * A thread-safe generic cache implementation using the First-In-First-Out eviction policy. + *

+ * The cache holds a fixed number of entries, defined by its capacity. When the cache is full and a + * new entry is added, the oldest entry in the cache is selected and evicted to make space. + *

+ * Optionally, entries can have a time-to-live (TTL) in milliseconds. If a TTL is set, entries will + * automatically expire and be removed upon access or insertion attempts. + *

+ * Features: + *

+ * + * @param the type of keys maintained by this cache + * @param the type of mapped values + * See FIFO + * @author Kevin Babu (GitHub) + */ +public final class FIFOCache { + + private final int capacity; + private final long defaultTTL; + private final Map> cache; + private final Lock lock; + + private long hits = 0; + private long misses = 0; + private final BiConsumer evictionListener; + private final EvictionStrategy evictionStrategy; + + /** + * Internal structure to store value + expiry timestamp. + * + * @param the type of the value being cached + */ + private static class CacheEntry { + V value; + long expiryTime; + + /** + * Constructs a new {@code CacheEntry} with the specified value and time-to-live (TTL). + * If TTL is 0, the entry is kept indefinitely, that is, unless it is the first value, + * then it will be removed according to the FIFO principle + * + * @param value the value to cache + * @param ttlMillis the time-to-live in milliseconds + */ + CacheEntry(V value, long ttlMillis) { + this.value = value; + if (ttlMillis == 0) { + this.expiryTime = Long.MAX_VALUE; + } else { + this.expiryTime = System.currentTimeMillis() + ttlMillis; + } + } + + /** + * Checks if the cache entry has expired. + * + * @return {@code true} if the current time is past the expiration time; {@code false} otherwise + */ + boolean isExpired() { + return System.currentTimeMillis() > expiryTime; + } + } + + /** + * Constructs a new {@code FIFOCache} instance using the provided {@link Builder}. + * + *

This constructor initializes the cache with the specified capacity and default TTL, + * sets up internal data structures (a {@code LinkedHashMap} for cache entries and configures eviction. + * + * @param builder the {@code Builder} object containing configuration parameters + */ + private FIFOCache(Builder builder) { + this.capacity = builder.capacity; + this.defaultTTL = builder.defaultTTL; + this.cache = new LinkedHashMap<>(); + this.lock = new ReentrantLock(); + this.evictionListener = builder.evictionListener; + this.evictionStrategy = builder.evictionStrategy; + } + + /** + * Retrieves the value associated with the specified key from the cache. + * + *

If the key is not present or the corresponding entry has expired, this method + * returns {@code null}. If an expired entry is found, it will be removed and the + * eviction listener (if any) will be notified. Cache hit-and-miss statistics are + * also updated accordingly. + * + * @param key the key whose associated value is to be returned; must not be {@code null} + * @return the cached value associated with the key, or {@code null} if not present or expired + * @throws IllegalArgumentException if {@code key} is {@code null} + */ + public V get(K key) { + if (key == null) { + throw new IllegalArgumentException("Key must not be null"); + } + + lock.lock(); + try { + evictionStrategy.onAccess(this); + + CacheEntry entry = cache.get(key); + if (entry == null || entry.isExpired()) { + if (entry != null) { + cache.remove(key); + notifyEviction(key, entry.value); + } + misses++; + return null; + } + hits++; + return entry.value; + } finally { + lock.unlock(); + } + } + + /** + * Adds a key-value pair to the cache using the default time-to-live (TTL). + * + *

The key may overwrite an existing entry. The actual insertion is delegated + * to the overloaded {@link #put(K, V, long)} method. + * + * @param key the key to cache the value under + * @param value the value to be cached + */ + public void put(K key, V value) { + put(key, value, defaultTTL); + } + + /** + * Adds a key-value pair to the cache with a specified time-to-live (TTL). + * + *

If the key already exists, its value is removed, re-inserted at tail and its TTL is reset. + * If the key does not exist and the cache is full, the oldest entry is evicted to make space. + * Expired entries are also cleaned up prior to any eviction. The eviction listener + * is notified when an entry gets evicted. + * + * @param key the key to associate with the cached value; must not be {@code null} + * @param value the value to be cached; must not be {@code null} + * @param ttlMillis the time-to-live for this entry in milliseconds; must be >= 0 + * @throws IllegalArgumentException if {@code key} or {@code value} is {@code null}, or if {@code ttlMillis} is negative + */ + public void put(K key, V value, long ttlMillis) { + if (key == null || value == null) { + throw new IllegalArgumentException("Key and value must not be null"); + } + if (ttlMillis < 0) { + throw new IllegalArgumentException("TTL must be >= 0"); + } + + lock.lock(); + try { + // If key already exists, remove it + CacheEntry oldEntry = cache.remove(key); + if (oldEntry != null && !oldEntry.isExpired()) { + notifyEviction(key, oldEntry.value); + } + + // Evict expired entries to make space for new entry + evictExpired(); + + // If no expired entry was removed, remove the oldest + if (cache.size() >= capacity) { + Iterator>> it = cache.entrySet().iterator(); + if (it.hasNext()) { + Map.Entry> eldest = it.next(); + it.remove(); + notifyEviction(eldest.getKey(), eldest.getValue().value); + } + } + + // Insert new entry at tail + cache.put(key, new CacheEntry<>(value, ttlMillis)); + } finally { + lock.unlock(); + } + } + + /** + * Removes all expired entries from the cache. + * + *

This method iterates through the list of cached keys and checks each associated + * entry for expiration. Expired entries are removed the cache map. For each eviction, + * the eviction listener is notified. + */ + private int evictExpired() { + int count = 0; + Iterator>> it = cache.entrySet().iterator(); + + while (it.hasNext()) { + Map.Entry> entry = it.next(); + if (entry != null && entry.getValue().isExpired()) { + it.remove(); + notifyEviction(entry.getKey(), entry.getValue().value); + count++; + } + } + + return count; + } + + /** + * Removes the specified key and its associated entry from the cache. + * + * @param key the key to remove from the cache; + * @return the value associated with the key; or {@code null} if no such key exists + */ + public V removeKey(K key) { + if (key == null) { + throw new IllegalArgumentException("Key cannot be null"); + } + CacheEntry entry = cache.remove(key); + + // No such key in cache + if (entry == null) { + return null; + } + + notifyEviction(key, entry.value); + return entry.value; + } + + /** + * Notifies the eviction listener, if one is registered, that a key-value pair has been evicted. + * + *

If the {@code evictionListener} is not {@code null}, it is invoked with the provided key + * and value. Any exceptions thrown by the listener are caught and logged to standard error, + * preventing them from disrupting cache operations. + * + * @param key the key that was evicted + * @param value the value that was associated with the evicted key + */ + private void notifyEviction(K key, V value) { + if (evictionListener != null) { + try { + evictionListener.accept(key, value); + } catch (Exception e) { + System.err.println("Eviction listener failed: " + e.getMessage()); + } + } + } + + /** + * Returns the number of successful cache lookups (hits). + * + * @return the number of cache hits + */ + public long getHits() { + lock.lock(); + try { + return hits; + } finally { + lock.unlock(); + } + } + + /** + * Returns the number of failed cache lookups (misses), including expired entries. + * + * @return the number of cache misses + */ + public long getMisses() { + lock.lock(); + try { + return misses; + } finally { + lock.unlock(); + } + } + + /** + * Returns the current number of entries in the cache, excluding expired ones. + * + * @return the current cache size + */ + public int size() { + lock.lock(); + try { + evictionStrategy.onAccess(this); + + int count = 0; + for (CacheEntry entry : cache.values()) { + if (!entry.isExpired()) { + ++count; + } + } + return count; + } finally { + lock.unlock(); + } + } + + /** + * Removes all entries from the cache, regardless of their expiration status. + * + *

This method clears the internal cache map entirely, resets the hit-and-miss counters, + * and notifies the eviction listener (if any) for each removed entry. + * Note that expired entries are treated the same as active ones for the purpose of clearing. + * + *

This operation acquires the internal lock to ensure thread safety. + */ + public void clear() { + lock.lock(); + try { + for (Map.Entry> entry : cache.entrySet()) { + notifyEviction(entry.getKey(), entry.getValue().value); + } + cache.clear(); + hits = 0; + misses = 0; + } finally { + lock.unlock(); + } + } + + /** + * Returns a set of all keys currently stored in the cache that have not expired. + * + *

This method iterates through the cache and collects the keys of all non-expired entries. + * Expired entries are ignored but not removed. If you want to ensure expired entries are cleaned up, + * consider invoking {@link EvictionStrategy#onAccess(FIFOCache)} or calling {@link #evictExpired()} manually. + * + *

This operation acquires the internal lock to ensure thread safety. + * + * @return a set containing all non-expired keys currently in the cache + */ + public Set getAllKeys() { + lock.lock(); + try { + Set keys = new LinkedHashSet<>(); + + for (Map.Entry> entry : cache.entrySet()) { + if (!entry.getValue().isExpired()) { + keys.add(entry.getKey()); + } + } + + return keys; + } finally { + lock.unlock(); + } + } + + /** + * Returns the current {@link EvictionStrategy} used by this cache instance. + + * @return the eviction strategy currently assigned to this cache + */ + public EvictionStrategy getEvictionStrategy() { + return evictionStrategy; + } + + /** + * Returns a string representation of the cache, including metadata and current non-expired entries. + * + *

The returned string includes the cache's capacity, current size (excluding expired entries), + * hit-and-miss counts, and a map of all non-expired key-value pairs. This method acquires a lock + * to ensure thread-safe access. + * + * @return a string summarizing the state of the cache + */ + @Override + public String toString() { + lock.lock(); + try { + Map visible = new LinkedHashMap<>(); + for (Map.Entry> entry : cache.entrySet()) { + if (!entry.getValue().isExpired()) { + visible.put(entry.getKey(), entry.getValue().value); + } + } + return String.format("Cache(capacity=%d, size=%d, hits=%d, misses=%d, entries=%s)", capacity, visible.size(), hits, misses, visible); + } finally { + lock.unlock(); + } + } + + /** + * A strategy interface for controlling when expired entries are evicted from the cache. + * + *

Implementations decide whether and when to trigger {@link FIFOCache#evictExpired()} based + * on cache usage patterns. This allows for flexible eviction behaviour such as periodic cleanup, + * or no automatic cleanup. + * + * @param the type of keys maintained by the cache + * @param the type of cached values + */ + public interface EvictionStrategy { + /** + * Called on each cache access (e.g., {@link FIFOCache#get(Object)}) to optionally trigger eviction. + * + * @param cache the cache instance on which this strategy is applied + * @return the number of expired entries evicted during this access + */ + int onAccess(FIFOCache cache); + } + + /** + * An eviction strategy that performs eviction of expired entries on each call. + * + * @param the type of keys + * @param the type of values + */ + public static class ImmediateEvictionStrategy implements EvictionStrategy { + @Override + public int onAccess(FIFOCache cache) { + return cache.evictExpired(); + } + } + + /** + * An eviction strategy that triggers eviction on every fixed number of accesses. + * + *

This deterministic strategy ensures cleanup occurs at predictable intervals, + * ideal for moderately active caches where memory usage is a concern. + * + * @param the type of keys + * @param the type of values + */ + public static class PeriodicEvictionStrategy implements EvictionStrategy { + private final int interval; + private final AtomicInteger counter = new AtomicInteger(); + + /** + * Constructs a periodic eviction strategy. + * + * @param interval the number of accesses between evictions; must be > 0 + * @throws IllegalArgumentException if {@code interval} is less than or equal to 0 + */ + public PeriodicEvictionStrategy(int interval) { + if (interval <= 0) { + throw new IllegalArgumentException("Interval must be > 0"); + } + this.interval = interval; + } + + @Override + public int onAccess(FIFOCache cache) { + if (counter.incrementAndGet() % interval == 0) { + return cache.evictExpired(); + } + + return 0; + } + } + + /** + * A builder for constructing a {@link FIFOCache} instance with customizable settings. + * + *

Allows configuring capacity, default TTL, eviction listener, and a pluggable eviction + * strategy. Call {@link #build()} to create the configured cache instance. + * + * @param the type of keys maintained by the cache + * @param the type of values stored in the cache + */ + public static class Builder { + private final int capacity; + private long defaultTTL = 0; + private BiConsumer evictionListener; + private EvictionStrategy evictionStrategy = new FIFOCache.ImmediateEvictionStrategy<>(); + /** + * Creates a new {@code Builder} with the specified cache capacity. + * + * @param capacity the maximum number of entries the cache can hold; must be > 0 + * @throws IllegalArgumentException if {@code capacity} is less than or equal to 0 + */ + public Builder(int capacity) { + if (capacity <= 0) { + throw new IllegalArgumentException("Capacity must be > 0"); + } + this.capacity = capacity; + } + + /** + * Sets the default time-to-live (TTL) in milliseconds for cache entries. + * + * @param ttlMillis the TTL duration in milliseconds; must be >= 0 + * @return this builder instance for chaining + * @throws IllegalArgumentException if {@code ttlMillis} is negative + */ + public Builder defaultTTL(long ttlMillis) { + if (ttlMillis < 0) { + throw new IllegalArgumentException("Default TTL must be >= 0"); + } + this.defaultTTL = ttlMillis; + return this; + } + + /** + * Sets an eviction listener to be notified when entries are evicted from the cache. + * + * @param listener a {@link BiConsumer} that accepts evicted keys and values; must not be {@code null} + * @return this builder instance for chaining + * @throws IllegalArgumentException if {@code listener} is {@code null} + */ + public Builder evictionListener(BiConsumer listener) { + if (listener == null) { + throw new IllegalArgumentException("Listener must not be null"); + } + this.evictionListener = listener; + return this; + } + + /** + * Builds and returns a new {@link FIFOCache} instance with the configured parameters. + * + * @return a fully configured {@code FIFOCache} instance + */ + public FIFOCache build() { + return new FIFOCache<>(this); + } + + /** + * Sets the eviction strategy used to determine when to clean up expired entries. + * + * @param strategy an {@link EvictionStrategy} implementation; must not be {@code null} + * @return this builder instance + * @throws IllegalArgumentException if {@code strategy} is {@code null} + */ + public Builder evictionStrategy(EvictionStrategy strategy) { + if (strategy == null) { + throw new IllegalArgumentException("Eviction strategy must not be null"); + } + this.evictionStrategy = strategy; + return this; + } + } +} diff --git a/src/main/java/com/thealgorithms/datastructures/caches/RRCache.java b/src/main/java/com/thealgorithms/datastructures/caches/RRCache.java new file mode 100644 index 000000000000..1821872be9cd --- /dev/null +++ b/src/main/java/com/thealgorithms/datastructures/caches/RRCache.java @@ -0,0 +1,505 @@ +package com.thealgorithms.datastructures.caches; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Random; +import java.util.concurrent.locks.Lock; +import java.util.concurrent.locks.ReentrantLock; +import java.util.function.BiConsumer; + +/** + * A thread-safe generic cache implementation using the Random Replacement (RR) eviction policy. + *

+ * The cache holds a fixed number of entries, defined by its capacity. When the cache is full and a + * new entry is added, one of the existing entries is selected at random and evicted to make space. + *

+ * Optionally, entries can have a time-to-live (TTL) in milliseconds. If a TTL is set, entries will + * automatically expire and be removed upon access or insertion attempts. + *

+ * Features: + *

    + *
  • Random eviction when capacity is exceeded
    • + *
  • Optional TTL (time-to-live in milliseconds) per entry or default TTL for all entries
    • + *
  • Thread-safe access using locking
    • + *
  • Hit and miss counters for cache statistics
    • + *
  • Eviction listener callback support
    • + *
+ * + * @param the type of keys maintained by this cache + * @param the type of mapped values + * See Random Replacement + * @author Kevin Babu (GitHub) + */ +public final class RRCache { + + private final int capacity; + private final long defaultTTL; + private final Map> cache; + private final List keys; + private final Random random; + private final Lock lock; + + private long hits = 0; + private long misses = 0; + private final BiConsumer evictionListener; + private final EvictionStrategy evictionStrategy; + + /** + * Internal structure to store value + expiry timestamp. + * + * @param the type of the value being cached + */ + private static class CacheEntry { + V value; + long expiryTime; + + /** + * Constructs a new {@code CacheEntry} with the specified value and time-to-live (TTL). + * + * @param value the value to cache + * @param ttlMillis the time-to-live in milliseconds + */ + CacheEntry(V value, long ttlMillis) { + this.value = value; + this.expiryTime = System.currentTimeMillis() + ttlMillis; + } + + /** + * Checks if the cache entry has expired. + * + * @return {@code true} if the current time is past the expiration time; {@code false} otherwise + */ + boolean isExpired() { + return System.currentTimeMillis() > expiryTime; + } + } + + /** + * Constructs a new {@code RRCache} instance using the provided {@link Builder}. + * + *

This constructor initializes the cache with the specified capacity and default TTL, + * sets up internal data structures (a {@code HashMap} for cache entries and an {@code ArrayList} + * for key tracking), and configures eviction and randomization behavior. + * + * @param builder the {@code Builder} object containing configuration parameters + */ + private RRCache(Builder builder) { + this.capacity = builder.capacity; + this.defaultTTL = builder.defaultTTL; + this.cache = new HashMap<>(builder.capacity); + this.keys = new ArrayList<>(builder.capacity); + this.random = builder.random != null ? builder.random : new Random(); + this.lock = new ReentrantLock(); + this.evictionListener = builder.evictionListener; + this.evictionStrategy = builder.evictionStrategy; + } + + /** + * Retrieves the value associated with the specified key from the cache. + * + *

If the key is not present or the corresponding entry has expired, this method + * returns {@code null}. If an expired entry is found, it will be removed and the + * eviction listener (if any) will be notified. Cache hit-and-miss statistics are + * also updated accordingly. + * + * @param key the key whose associated value is to be returned; must not be {@code null} + * @return the cached value associated with the key, or {@code null} if not present or expired + * @throws IllegalArgumentException if {@code key} is {@code null} + */ + public V get(K key) { + if (key == null) { + throw new IllegalArgumentException("Key must not be null"); + } + + lock.lock(); + try { + evictionStrategy.onAccess(this); + + CacheEntry entry = cache.get(key); + if (entry == null || entry.isExpired()) { + if (entry != null) { + removeKey(key); + notifyEviction(key, entry.value); + } + misses++; + return null; + } + hits++; + return entry.value; + } finally { + lock.unlock(); + } + } + + /** + * Adds a key-value pair to the cache using the default time-to-live (TTL). + * + *

The key may overwrite an existing entry. The actual insertion is delegated + * to the overloaded {@link #put(K, V, long)} method. + * + * @param key the key to cache the value under + * @param value the value to be cached + */ + public void put(K key, V value) { + put(key, value, defaultTTL); + } + + /** + * Adds a key-value pair to the cache with a specified time-to-live (TTL). + * + *

If the key already exists, its value is updated and its TTL is reset. If the key + * does not exist and the cache is full, a random entry is evicted to make space. + * Expired entries are also cleaned up prior to any eviction. The eviction listener + * is notified when an entry gets evicted. + * + * @param key the key to associate with the cached value; must not be {@code null} + * @param value the value to be cached; must not be {@code null} + * @param ttlMillis the time-to-live for this entry in milliseconds; must be >= 0 + * @throws IllegalArgumentException if {@code key} or {@code value} is {@code null}, or if {@code ttlMillis} is negative + */ + public void put(K key, V value, long ttlMillis) { + if (key == null || value == null) { + throw new IllegalArgumentException("Key and value must not be null"); + } + if (ttlMillis < 0) { + throw new IllegalArgumentException("TTL must be >= 0"); + } + + lock.lock(); + try { + if (cache.containsKey(key)) { + cache.put(key, new CacheEntry<>(value, ttlMillis)); + return; + } + + evictExpired(); + + if (cache.size() >= capacity) { + int idx = random.nextInt(keys.size()); + K evictKey = keys.remove(idx); + CacheEntry evictVal = cache.remove(evictKey); + notifyEviction(evictKey, evictVal.value); + } + + cache.put(key, new CacheEntry<>(value, ttlMillis)); + keys.add(key); + } finally { + lock.unlock(); + } + } + + /** + * Removes all expired entries from the cache. + * + *

This method iterates through the list of cached keys and checks each associated + * entry for expiration. Expired entries are removed from both the key tracking list + * and the cache map. For each eviction, the eviction listener is notified. + */ + private int evictExpired() { + Iterator it = keys.iterator(); + int expiredCount = 0; + + while (it.hasNext()) { + K k = it.next(); + CacheEntry entry = cache.get(k); + if (entry != null && entry.isExpired()) { + it.remove(); + cache.remove(k); + ++expiredCount; + notifyEviction(k, entry.value); + } + } + return expiredCount; + } + + /** + * Removes the specified key and its associated entry from the cache. + * + *

This method deletes the key from both the cache map and the key tracking list. + * + * @param key the key to remove from the cache + */ + private void removeKey(K key) { + cache.remove(key); + keys.remove(key); + } + + /** + * Notifies the eviction listener, if one is registered, that a key-value pair has been evicted. + * + *

If the {@code evictionListener} is not {@code null}, it is invoked with the provided key + * and value. Any exceptions thrown by the listener are caught and logged to standard error, + * preventing them from disrupting cache operations. + * + * @param key the key that was evicted + * @param value the value that was associated with the evicted key + */ + private void notifyEviction(K key, V value) { + if (evictionListener != null) { + try { + evictionListener.accept(key, value); + } catch (Exception e) { + System.err.println("Eviction listener failed: " + e.getMessage()); + } + } + } + + /** + * Returns the number of successful cache lookups (hits). + * + * @return the number of cache hits + */ + public long getHits() { + lock.lock(); + try { + return hits; + } finally { + lock.unlock(); + } + } + + /** + * Returns the number of failed cache lookups (misses), including expired entries. + * + * @return the number of cache misses + */ + public long getMisses() { + lock.lock(); + try { + return misses; + } finally { + lock.unlock(); + } + } + + /** + * Returns the current number of entries in the cache, excluding expired ones. + * + * @return the current cache size + */ + public int size() { + lock.lock(); + try { + int cachedSize = cache.size(); + int evictedCount = evictionStrategy.onAccess(this); + if (evictedCount > 0) { + return cachedSize - evictedCount; + } + + // This runs if periodic eviction does not occur + int count = 0; + for (Map.Entry> entry : cache.entrySet()) { + if (!entry.getValue().isExpired()) { + ++count; + } + } + return count; + } finally { + lock.unlock(); + } + } + + /** + * Returns the current {@link EvictionStrategy} used by this cache instance. + + * @return the eviction strategy currently assigned to this cache + */ + public EvictionStrategy getEvictionStrategy() { + return evictionStrategy; + } + + /** + * Returns a string representation of the cache, including metadata and current non-expired entries. + * + *

The returned string includes the cache's capacity, current size (excluding expired entries), + * hit-and-miss counts, and a map of all non-expired key-value pairs. This method acquires a lock + * to ensure thread-safe access. + * + * @return a string summarizing the state of the cache + */ + @Override + public String toString() { + lock.lock(); + try { + Map visible = new HashMap<>(); + for (Map.Entry> entry : cache.entrySet()) { + if (!entry.getValue().isExpired()) { + visible.put(entry.getKey(), entry.getValue().value); + } + } + return String.format("Cache(capacity=%d, size=%d, hits=%d, misses=%d, entries=%s)", capacity, visible.size(), hits, misses, visible); + } finally { + lock.unlock(); + } + } + + /** + * A strategy interface for controlling when expired entries are evicted from the cache. + * + *

Implementations decide whether and when to trigger {@link RRCache#evictExpired()} based + * on cache usage patterns. This allows for flexible eviction behaviour such as periodic cleanup, + * or no automatic cleanup. + * + * @param the type of keys maintained by the cache + * @param the type of cached values + */ + public interface EvictionStrategy { + /** + * Called on each cache access (e.g., {@link RRCache#get(Object)}) to optionally trigger eviction. + * + * @param cache the cache instance on which this strategy is applied + * @return the number of expired entries evicted during this access + */ + int onAccess(RRCache cache); + } + + /** + * An eviction strategy that performs eviction of expired entries on each call. + * + * @param the type of keys + * @param the type of values + */ + public static class NoEvictionStrategy implements EvictionStrategy { + @Override + public int onAccess(RRCache cache) { + return cache.evictExpired(); + } + } + + /** + * An eviction strategy that triggers eviction every fixed number of accesses. + * + *

This deterministic strategy ensures cleanup occurs at predictable intervals, + * ideal for moderately active caches where memory usage is a concern. + * + * @param the type of keys + * @param the type of values + */ + public static class PeriodicEvictionStrategy implements EvictionStrategy { + private final int interval; + private int counter = 0; + + /** + * Constructs a periodic eviction strategy. + * + * @param interval the number of accesses between evictions; must be > 0 + * @throws IllegalArgumentException if {@code interval} is less than or equal to 0 + */ + public PeriodicEvictionStrategy(int interval) { + if (interval <= 0) { + throw new IllegalArgumentException("Interval must be > 0"); + } + this.interval = interval; + } + + @Override + public int onAccess(RRCache cache) { + if (++counter % interval == 0) { + return cache.evictExpired(); + } + + return 0; + } + } + + /** + * A builder for constructing an {@link RRCache} instance with customizable settings. + * + *

Allows configuring capacity, default TTL, random eviction behavior, eviction listener, + * and a pluggable eviction strategy. Call {@link #build()} to create the configured cache instance. + * + * @param the type of keys maintained by the cache + * @param the type of values stored in the cache + */ + public static class Builder { + private final int capacity; + private long defaultTTL = 0; + private Random random; + private BiConsumer evictionListener; + private EvictionStrategy evictionStrategy = new RRCache.PeriodicEvictionStrategy<>(100); + /** + * Creates a new {@code Builder} with the specified cache capacity. + * + * @param capacity the maximum number of entries the cache can hold; must be > 0 + * @throws IllegalArgumentException if {@code capacity} is less than or equal to 0 + */ + public Builder(int capacity) { + if (capacity <= 0) { + throw new IllegalArgumentException("Capacity must be > 0"); + } + this.capacity = capacity; + } + + /** + * Sets the default time-to-live (TTL) in milliseconds for cache entries. + * + * @param ttlMillis the TTL duration in milliseconds; must be >= 0 + * @return this builder instance for chaining + * @throws IllegalArgumentException if {@code ttlMillis} is negative + */ + public Builder defaultTTL(long ttlMillis) { + if (ttlMillis < 0) { + throw new IllegalArgumentException("Default TTL must be >= 0"); + } + this.defaultTTL = ttlMillis; + return this; + } + + /** + * Sets the {@link Random} instance to be used for random eviction selection. + * + * @param r a non-null {@code Random} instance + * @return this builder instance for chaining + * @throws IllegalArgumentException if {@code r} is {@code null} + */ + public Builder random(Random r) { + if (r == null) { + throw new IllegalArgumentException("Random must not be null"); + } + this.random = r; + return this; + } + + /** + * Sets an eviction listener to be notified when entries are evicted from the cache. + * + * @param listener a {@link BiConsumer} that accepts evicted keys and values; must not be {@code null} + * @return this builder instance for chaining + * @throws IllegalArgumentException if {@code listener} is {@code null} + */ + public Builder evictionListener(BiConsumer listener) { + if (listener == null) { + throw new IllegalArgumentException("Listener must not be null"); + } + this.evictionListener = listener; + return this; + } + + /** + * Builds and returns a new {@link RRCache} instance with the configured parameters. + * + * @return a fully configured {@code RRCache} instance + */ + public RRCache build() { + return new RRCache<>(this); + } + + /** + * Sets the eviction strategy used to determine when to clean up expired entries. + * + * @param strategy an {@link EvictionStrategy} implementation; must not be {@code null} + * @return this builder instance + * @throws IllegalArgumentException if {@code strategy} is {@code null} + */ + public Builder evictionStrategy(EvictionStrategy strategy) { + if (strategy == null) { + throw new IllegalArgumentException("Eviction strategy must not be null"); + } + this.evictionStrategy = strategy; + return this; + } + } +} diff --git a/src/main/java/com/thealgorithms/randomized/RandomizedClosestPair.java b/src/main/java/com/thealgorithms/randomized/RandomizedClosestPair.java new file mode 100644 index 000000000000..616f7fb7d7cf --- /dev/null +++ b/src/main/java/com/thealgorithms/randomized/RandomizedClosestPair.java @@ -0,0 +1,113 @@ +package com.thealgorithms.randomized; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collections; +import java.util.Comparator; +import java.util.List; +import java.util.Random; + +/** + * Randomized Closest Pair of Points Algorithm + * + * Use Case: + * - Efficiently finds the closest pair of points in a 2D plane. + * - Applicable in computational geometry, clustering, and graphics. + * + * Time Complexity: + * - Expected: O(n log n) using randomized divide and conquer + * + * @see Closest Pair of Points - Wikipedia + */ +public final class RandomizedClosestPair { + + // Prevent instantiation of utility class + private RandomizedClosestPair() { + throw new UnsupportedOperationException("Utility class"); + } + + public static class Point { + public final double x; + public final double y; + + public Point(double x, double y) { + this.x = x; + this.y = y; + } + } + + public static double findClosestPairDistance(Point[] points) { + List shuffled = new ArrayList<>(Arrays.asList(points)); + Collections.shuffle(shuffled, new Random()); + + Point[] px = shuffled.toArray(new Point[0]); + Arrays.sort(px, Comparator.comparingDouble(p -> p.x)); + + Point[] py = px.clone(); + Arrays.sort(py, Comparator.comparingDouble(p -> p.y)); + + return closestPair(px, py); + } + + private static double closestPair(Point[] px, Point[] py) { + int n = px.length; + if (n <= 3) { + return bruteForce(px); + } + + int mid = n / 2; + Point midPoint = px[mid]; + + Point[] qx = Arrays.copyOfRange(px, 0, mid); + Point[] rx = Arrays.copyOfRange(px, mid, n); + + List qy = new ArrayList<>(); + List ry = new ArrayList<>(); + for (Point p : py) { + if (p.x <= midPoint.x) { + qy.add(p); + } else { + ry.add(p); + } + } + + double d1 = closestPair(qx, qy.toArray(new Point[0])); + double d2 = closestPair(rx, ry.toArray(new Point[0])); + + double d = Math.min(d1, d2); + + List strip = new ArrayList<>(); + for (Point p : py) { + if (Math.abs(p.x - midPoint.x) < d) { + strip.add(p); + } + } + + return Math.min(d, stripClosest(strip, d)); + } + + private static double bruteForce(Point[] points) { + double min = Double.POSITIVE_INFINITY; + for (int i = 0; i < points.length; i++) { + for (int j = i + 1; j < points.length; j++) { + min = Math.min(min, distance(points[i], points[j])); + } + } + return min; + } + + private static double stripClosest(List strip, double d) { + double min = d; + int n = strip.size(); + for (int i = 0; i < n; i++) { + for (int j = i + 1; j < n && (strip.get(j).y - strip.get(i).y) < min; j++) { + min = Math.min(min, distance(strip.get(i), strip.get(j))); + } + } + return min; + } + + private static double distance(Point p1, Point p2) { + return Math.hypot(p1.x - p2.x, p1.y - p2.y); + } +} diff --git a/src/main/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerification.java b/src/main/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerification.java new file mode 100644 index 000000000000..b5ac7076bfd6 --- /dev/null +++ b/src/main/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerification.java @@ -0,0 +1,64 @@ +package com.thealgorithms.randomized; + +import java.util.Random; + +public final class RandomizedMatrixMultiplicationVerification { + + private RandomizedMatrixMultiplicationVerification() { + // Prevent instantiation of utility class + } + + /** + * Verifies whether A × B == C using Freivalds' algorithm. + * @param A Left matrix + * @param B Right matrix + * @param C Product matrix to verify + * @param iterations Number of randomized checks + * @return true if likely A×B == C; false if definitely not + */ + public static boolean verify(int[][] a, int[][] b, int[][] c, int iterations) { + int n = a.length; + Random random = new Random(); + + for (int iter = 0; iter < iterations; iter++) { + // Step 1: Generate random 0/1 vector + int[] r = new int[n]; + for (int i = 0; i < n; i++) { + r[i] = random.nextInt(2); + } + + // Step 2: Compute br = b × r + int[] br = new int[n]; + for (int i = 0; i < n; i++) { + for (int j = 0; j < n; j++) { + br[i] += b[i][j] * r[j]; + } + } + + // Step 3: Compute a(br) + int[] abr = new int[n]; + for (int i = 0; i < n; i++) { + for (int j = 0; j < n; j++) { + abr[i] += a[i][j] * br[j]; + } + } + + // Step 4: Compute cr = c × r + int[] cr = new int[n]; + for (int i = 0; i < n; i++) { + for (int j = 0; j < n; j++) { + cr[i] += c[i][j] * r[j]; + } + } + + // Step 5: Compare abr and cr + for (int i = 0; i < n; i++) { + if (abr[i] != cr[i]) { + return false; + } + } + } + + return true; + } +} diff --git a/src/test/java/com/thealgorithms/datastructures/caches/FIFOCacheTest.java b/src/test/java/com/thealgorithms/datastructures/caches/FIFOCacheTest.java new file mode 100644 index 000000000000..5f250e6ca3fd --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/caches/FIFOCacheTest.java @@ -0,0 +1,330 @@ +package com.thealgorithms.datastructures.caches; + +import java.util.ArrayList; +import java.util.HashSet; +import java.util.List; +import java.util.Set; +import java.util.concurrent.atomic.AtomicInteger; +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.BeforeEach; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.function.Executable; + +class FIFOCacheTest { + private FIFOCache cache; + private Set evictedKeys; + private List evictedValues; + + @BeforeEach + void setUp() { + evictedKeys = new HashSet<>(); + evictedValues = new ArrayList<>(); + + cache = new FIFOCache.Builder(3) + .defaultTTL(1000) + .evictionListener((k, v) -> { + evictedKeys.add(k); + evictedValues.add(v); + }) + .build(); + } + + @Test + void testPutAndGet() { + cache.put("a", "apple"); + Assertions.assertEquals("apple", cache.get("a")); + } + + @Test + void testOverwriteValue() { + cache.put("a", "apple"); + cache.put("a", "avocado"); + Assertions.assertEquals("avocado", cache.get("a")); + } + + @Test + void testExpiration() throws InterruptedException { + cache.put("temp", "value", 100); + Thread.sleep(200); + Assertions.assertNull(cache.get("temp")); + Assertions.assertTrue(evictedKeys.contains("temp")); + } + + @Test + void testEvictionOnCapacity() { + cache.put("a", "alpha"); + cache.put("b", "bravo"); + cache.put("c", "charlie"); + cache.put("d", "delta"); + + int size = cache.size(); + Assertions.assertEquals(3, size); + Assertions.assertEquals(1, evictedKeys.size()); + Assertions.assertEquals(1, evictedValues.size()); + } + + @Test + void testEvictionListener() { + cache.put("x", "one"); + cache.put("y", "two"); + cache.put("z", "three"); + cache.put("w", "four"); + + Assertions.assertFalse(evictedKeys.isEmpty()); + Assertions.assertFalse(evictedValues.isEmpty()); + } + + @Test + void testHitsAndMisses() { + cache.put("a", "apple"); + Assertions.assertEquals("apple", cache.get("a")); + Assertions.assertNull(cache.get("b")); + Assertions.assertEquals(1, cache.getHits()); + Assertions.assertEquals(1, cache.getMisses()); + } + + @Test + void testSizeExcludesExpired() throws InterruptedException { + cache.put("a", "a", 100); + cache.put("b", "b", 100); + cache.put("c", "c", 100); + Thread.sleep(150); + Assertions.assertEquals(0, cache.size()); + } + + @Test + void testSizeIncludesFresh() { + cache.put("a", "a", 1000); + cache.put("b", "b", 1000); + cache.put("c", "c", 1000); + Assertions.assertEquals(3, cache.size()); + } + + @Test + void testToStringDoesNotExposeExpired() throws InterruptedException { + cache.put("live", "alive"); + cache.put("dead", "gone", 100); + Thread.sleep(150); + String result = cache.toString(); + Assertions.assertTrue(result.contains("live")); + Assertions.assertFalse(result.contains("dead")); + } + + @Test + void testNullKeyGetThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.get(null)); + } + + @Test + void testPutNullKeyThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put(null, "v")); + } + + @Test + void testPutNullValueThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", null)); + } + + @Test + void testPutNegativeTTLThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", "v", -1)); + } + + @Test + void testBuilderNegativeCapacityThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> new FIFOCache.Builder<>(0)); + } + + @Test + void testBuilderNullEvictionListenerThrows() { + FIFOCache.Builder builder = new FIFOCache.Builder<>(1); + Assertions.assertThrows(IllegalArgumentException.class, () -> builder.evictionListener(null)); + } + + @Test + void testEvictionListenerExceptionDoesNotCrash() { + FIFOCache listenerCache = new FIFOCache.Builder(1).evictionListener((k, v) -> { throw new RuntimeException("Exception"); }).build(); + + listenerCache.put("a", "a"); + listenerCache.put("b", "b"); + Assertions.assertDoesNotThrow(() -> listenerCache.get("a")); + } + + @Test + void testTtlZeroThrowsIllegalArgumentException() { + Executable exec = () -> new FIFOCache.Builder(3).defaultTTL(-1).build(); + Assertions.assertThrows(IllegalArgumentException.class, exec); + } + + @Test + void testPeriodicEvictionStrategyEvictsAtInterval() throws InterruptedException { + FIFOCache periodicCache = new FIFOCache.Builder(10).defaultTTL(50).evictionStrategy(new FIFOCache.PeriodicEvictionStrategy<>(3)).build(); + + periodicCache.put("x", "1"); + Thread.sleep(100); + int ev1 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + int ev2 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + int ev3 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + + Assertions.assertEquals(0, ev1); + Assertions.assertEquals(0, ev2); + Assertions.assertEquals(1, ev3, "Eviction should happen on the 3rd access"); + Assertions.assertEquals(0, periodicCache.size()); + } + + @Test + void testPeriodicEvictionStrategyThrowsExceptionIfIntervalLessThanOrEqual0() { + Executable executable = () -> new FIFOCache.Builder(10).defaultTTL(50).evictionStrategy(new FIFOCache.PeriodicEvictionStrategy<>(0)).build(); + + Assertions.assertThrows(IllegalArgumentException.class, executable); + } + + @Test + void testImmediateEvictionStrategyStrategyEvictsOnEachCall() throws InterruptedException { + FIFOCache immediateEvictionStrategy = new FIFOCache.Builder(10).defaultTTL(50).evictionStrategy(new FIFOCache.ImmediateEvictionStrategy<>()).build(); + + immediateEvictionStrategy.put("x", "1"); + Thread.sleep(100); + int evicted = immediateEvictionStrategy.getEvictionStrategy().onAccess(immediateEvictionStrategy); + + Assertions.assertEquals(1, evicted); + } + + @Test + void testBuilderThrowsExceptionIfEvictionStrategyNull() { + Executable executable = () -> new FIFOCache.Builder(10).defaultTTL(50).evictionStrategy(null).build(); + + Assertions.assertThrows(IllegalArgumentException.class, executable); + } + + @Test + void testReturnsCorrectStrategyInstance() { + FIFOCache.EvictionStrategy strategy = new FIFOCache.ImmediateEvictionStrategy<>(); + + FIFOCache newCache = new FIFOCache.Builder(10).defaultTTL(1000).evictionStrategy(strategy).build(); + + Assertions.assertSame(strategy, newCache.getEvictionStrategy(), "Returned strategy should be the same instance"); + } + + @Test + void testDefaultStrategyIsImmediateEvictionStrategy() { + FIFOCache newCache = new FIFOCache.Builder(5).defaultTTL(1000).build(); + + Assertions.assertTrue(newCache.getEvictionStrategy() instanceof FIFOCache.ImmediateEvictionStrategy, "Default strategy should be ImmediateEvictionStrategyStrategy"); + } + + @Test + void testGetEvictionStrategyIsNotNull() { + FIFOCache newCache = new FIFOCache.Builder(5).build(); + + Assertions.assertNotNull(newCache.getEvictionStrategy(), "Eviction strategy should never be null"); + } + + @Test + void testRemoveKeyRemovesExistingKey() { + cache.put("A", "Alpha"); + cache.put("B", "Beta"); + + Assertions.assertEquals("Alpha", cache.get("A")); + Assertions.assertEquals("Beta", cache.get("B")); + + String removed = cache.removeKey("A"); + Assertions.assertEquals("Alpha", removed); + + Assertions.assertNull(cache.get("A")); + Assertions.assertEquals(1, cache.size()); + } + + @Test + void testRemoveKeyReturnsNullIfKeyNotPresent() { + cache.put("X", "X-ray"); + + Assertions.assertNull(cache.removeKey("NonExistent")); + Assertions.assertEquals(1, cache.size()); + } + + @Test + void testRemoveKeyHandlesExpiredEntry() throws InterruptedException { + FIFOCache expiringCache = new FIFOCache.Builder(2).defaultTTL(100).evictionStrategy(new FIFOCache.ImmediateEvictionStrategy<>()).build(); + + expiringCache.put("T", "Temporary"); + + Thread.sleep(200); + + String removed = expiringCache.removeKey("T"); + Assertions.assertEquals("Temporary", removed); + Assertions.assertNull(expiringCache.get("T")); + } + + @Test + void testRemoveKeyThrowsIfKeyIsNull() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.removeKey(null)); + } + + @Test + void testRemoveKeyTriggersEvictionListener() { + AtomicInteger evictedCount = new AtomicInteger(); + + FIFOCache localCache = new FIFOCache.Builder(2).evictionListener((key, value) -> evictedCount.incrementAndGet()).build(); + + localCache.put("A", "Apple"); + localCache.put("B", "Banana"); + + localCache.removeKey("A"); + + Assertions.assertEquals(1, evictedCount.get(), "Eviction listener should have been called once"); + } + + @Test + void testRemoveKeyDoestNotAffectOtherKeys() { + cache.put("A", "Alpha"); + cache.put("B", "Beta"); + cache.put("C", "Gamma"); + + cache.removeKey("B"); + + Assertions.assertEquals("Alpha", cache.get("A")); + Assertions.assertNull(cache.get("B")); + Assertions.assertEquals("Gamma", cache.get("C")); + } + + @Test + void testEvictionListenerExceptionDoesNotPropagate() { + FIFOCache localCache = new FIFOCache.Builder(1).evictionListener((key, value) -> { throw new RuntimeException(); }).build(); + + localCache.put("A", "Apple"); + + Assertions.assertDoesNotThrow(() -> localCache.put("B", "Beta")); + } + + @Test + void testGetKeysReturnsAllFreshKeys() { + cache.put("A", "Alpha"); + cache.put("B", "Beta"); + cache.put("G", "Gamma"); + + Set expectedKeys = Set.of("A", "B", "G"); + Assertions.assertEquals(expectedKeys, cache.getAllKeys()); + } + + @Test + void testGetKeysIgnoresExpiredKeys() throws InterruptedException { + cache.put("A", "Alpha"); + cache.put("B", "Beta"); + cache.put("G", "Gamma", 100); + + Set expectedKeys = Set.of("A", "B"); + Thread.sleep(200); + Assertions.assertEquals(expectedKeys, cache.getAllKeys()); + } + + @Test + void testClearRemovesAllEntries() { + cache.put("A", "Alpha"); + cache.put("B", "Beta"); + cache.put("G", "Gamma"); + + cache.clear(); + Assertions.assertEquals(0, cache.size()); + } +} diff --git a/src/test/java/com/thealgorithms/datastructures/caches/RRCacheTest.java b/src/test/java/com/thealgorithms/datastructures/caches/RRCacheTest.java new file mode 100644 index 000000000000..100c73ea2a5b --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/caches/RRCacheTest.java @@ -0,0 +1,222 @@ +package com.thealgorithms.datastructures.caches; + +import java.util.ArrayList; +import java.util.HashSet; +import java.util.List; +import java.util.Random; +import java.util.Set; +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.BeforeEach; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.function.Executable; + +class RRCacheTest { + + private RRCache cache; + private Set evictedKeys; + private List evictedValues; + + @BeforeEach + void setUp() { + evictedKeys = new HashSet<>(); + evictedValues = new ArrayList<>(); + + cache = new RRCache.Builder(3) + .defaultTTL(1000) + .random(new Random(0)) + .evictionListener((k, v) -> { + evictedKeys.add(k); + evictedValues.add(v); + }) + .build(); + } + + @Test + void testPutAndGet() { + cache.put("a", "apple"); + Assertions.assertEquals("apple", cache.get("a")); + } + + @Test + void testOverwriteValue() { + cache.put("a", "apple"); + cache.put("a", "avocado"); + Assertions.assertEquals("avocado", cache.get("a")); + } + + @Test + void testExpiration() throws InterruptedException { + cache.put("temp", "value", 100); // short TTL + Thread.sleep(200); + Assertions.assertNull(cache.get("temp")); + Assertions.assertTrue(evictedKeys.contains("temp")); + } + + @Test + void testEvictionOnCapacity() { + cache.put("a", "alpha"); + cache.put("b", "bravo"); + cache.put("c", "charlie"); + cache.put("d", "delta"); // triggers eviction + + int size = cache.size(); + Assertions.assertEquals(3, size); + Assertions.assertEquals(1, evictedKeys.size()); + Assertions.assertEquals(1, evictedValues.size()); + } + + @Test + void testEvictionListener() { + cache.put("x", "one"); + cache.put("y", "two"); + cache.put("z", "three"); + cache.put("w", "four"); // one of x, y, z will be evicted + + Assertions.assertFalse(evictedKeys.isEmpty()); + Assertions.assertFalse(evictedValues.isEmpty()); + } + + @Test + void testHitsAndMisses() { + cache.put("a", "apple"); + Assertions.assertEquals("apple", cache.get("a")); + Assertions.assertNull(cache.get("b")); + Assertions.assertEquals(1, cache.getHits()); + Assertions.assertEquals(1, cache.getMisses()); + } + + @Test + void testSizeExcludesExpired() throws InterruptedException { + cache.put("a", "a", 100); + cache.put("b", "b", 100); + cache.put("c", "c", 100); + Thread.sleep(150); + Assertions.assertEquals(0, cache.size()); + } + + @Test + void testToStringDoesNotExposeExpired() throws InterruptedException { + cache.put("live", "alive"); + cache.put("dead", "gone", 100); + Thread.sleep(150); + String result = cache.toString(); + Assertions.assertTrue(result.contains("live")); + Assertions.assertFalse(result.contains("dead")); + } + + @Test + void testNullKeyGetThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.get(null)); + } + + @Test + void testPutNullKeyThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put(null, "v")); + } + + @Test + void testPutNullValueThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", null)); + } + + @Test + void testPutNegativeTTLThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", "v", -1)); + } + + @Test + void testBuilderNegativeCapacityThrows() { + Assertions.assertThrows(IllegalArgumentException.class, () -> new RRCache.Builder<>(0)); + } + + @Test + void testBuilderNullRandomThrows() { + RRCache.Builder builder = new RRCache.Builder<>(1); + Assertions.assertThrows(IllegalArgumentException.class, () -> builder.random(null)); + } + + @Test + void testBuilderNullEvictionListenerThrows() { + RRCache.Builder builder = new RRCache.Builder<>(1); + Assertions.assertThrows(IllegalArgumentException.class, () -> builder.evictionListener(null)); + } + + @Test + void testEvictionListenerExceptionDoesNotCrash() { + RRCache listenerCache = new RRCache.Builder(1).evictionListener((k, v) -> { throw new RuntimeException("Exception"); }).build(); + + listenerCache.put("a", "a"); + listenerCache.put("b", "b"); // causes eviction but should not crash + Assertions.assertDoesNotThrow(() -> listenerCache.get("a")); + } + + @Test + void testTtlZeroThrowsIllegalArgumentException() { + Executable exec = () -> new RRCache.Builder(3).defaultTTL(-1).build(); + Assertions.assertThrows(IllegalArgumentException.class, exec); + } + + @Test + void testPeriodicEvictionStrategyEvictsAtInterval() throws InterruptedException { + RRCache periodicCache = new RRCache.Builder(10).defaultTTL(50).evictionStrategy(new RRCache.PeriodicEvictionStrategy<>(3)).build(); + + periodicCache.put("x", "1"); + Thread.sleep(100); + int ev1 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + int ev2 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + int ev3 = periodicCache.getEvictionStrategy().onAccess(periodicCache); + + Assertions.assertEquals(0, ev1); + Assertions.assertEquals(0, ev2); + Assertions.assertEquals(1, ev3, "Eviction should happen on the 3rd access"); + Assertions.assertEquals(0, periodicCache.size()); + } + + @Test + void testPeriodicEvictionStrategyThrowsExceptionIfIntervalLessThanOrEqual0() { + Executable executable = () -> new RRCache.Builder(10).defaultTTL(50).evictionStrategy(new RRCache.PeriodicEvictionStrategy<>(0)).build(); + + Assertions.assertThrows(IllegalArgumentException.class, executable); + } + + @Test + void testNoEvictionStrategyEvictsOnEachCall() throws InterruptedException { + RRCache noEvictionStrategyCache = new RRCache.Builder(10).defaultTTL(50).evictionStrategy(new RRCache.NoEvictionStrategy<>()).build(); + + noEvictionStrategyCache.put("x", "1"); + Thread.sleep(100); + int evicted = noEvictionStrategyCache.getEvictionStrategy().onAccess(noEvictionStrategyCache); + + Assertions.assertEquals(1, evicted); + } + + @Test + void testBuilderThrowsExceptionIfEvictionStrategyNull() { + Executable executable = () -> new RRCache.Builder(10).defaultTTL(50).evictionStrategy(null).build(); + + Assertions.assertThrows(IllegalArgumentException.class, executable); + } + + @Test + void testReturnsCorrectStrategyInstance() { + RRCache.EvictionStrategy strategy = new RRCache.NoEvictionStrategy<>(); + + RRCache newCache = new RRCache.Builder(10).defaultTTL(1000).evictionStrategy(strategy).build(); + + Assertions.assertSame(strategy, newCache.getEvictionStrategy(), "Returned strategy should be the same instance"); + } + + @Test + void testDefaultStrategyIsNoEviction() { + RRCache newCache = new RRCache.Builder(5).defaultTTL(1000).build(); + + Assertions.assertTrue(newCache.getEvictionStrategy() instanceof RRCache.PeriodicEvictionStrategy, "Default strategy should be NoEvictionStrategy"); + } + + @Test + void testGetEvictionStrategyIsNotNull() { + RRCache newCache = new RRCache.Builder(5).build(); + + Assertions.assertNotNull(newCache.getEvictionStrategy(), "Eviction strategy should never be null"); + } +} diff --git a/src/test/java/com/thealgorithms/randomized/RandomizedClosestPairTest.java b/src/test/java/com/thealgorithms/randomized/RandomizedClosestPairTest.java new file mode 100644 index 000000000000..fd739b743989 --- /dev/null +++ b/src/test/java/com/thealgorithms/randomized/RandomizedClosestPairTest.java @@ -0,0 +1,30 @@ +package com.thealgorithms.randomized; + +import static org.junit.jupiter.api.Assertions.assertEquals; + +import com.thealgorithms.randomized.RandomizedClosestPair.Point; +import org.junit.jupiter.api.Test; + +public class RandomizedClosestPairTest { + + @Test + public void testFindClosestPairDistance() { + Point[] points = {new Point(1, 1), new Point(2, 2), new Point(3, 3), new Point(8, 8), new Point(13, 13)}; + double result = RandomizedClosestPair.findClosestPairDistance(points); + assertEquals(Math.sqrt(2), result, 0.00001); + } + + @Test + public void testWithIdenticalPoints() { + Point[] points = {new Point(0, 0), new Point(0, 0), new Point(1, 1)}; + double result = RandomizedClosestPair.findClosestPairDistance(points); + assertEquals(0.0, result, 0.00001); + } + + @Test + public void testWithDistantPoints() { + Point[] points = {new Point(0, 0), new Point(5, 0), new Point(10, 0)}; + double result = RandomizedClosestPair.findClosestPairDistance(points); + assertEquals(5.0, result, 0.00001); + } +} diff --git a/src/test/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerificationTest.java b/src/test/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerificationTest.java new file mode 100644 index 000000000000..330662ac2c52 --- /dev/null +++ b/src/test/java/com/thealgorithms/randomized/RandomizedMatrixMultiplicationVerificationTest.java @@ -0,0 +1,41 @@ +package com.thealgorithms.randomized; + +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import org.junit.jupiter.api.Test; + +class RandomizedMatrixMultiplicationVerificationTest { + + @Test + void testCorrectMultiplication() { + int[][] a = {{1, 2}, {3, 4}}; + int[][] b = {{5, 6}, {7, 8}}; + int[][] c = {{19, 22}, {43, 50}}; + assertTrue(RandomizedMatrixMultiplicationVerification.verify(a, b, c, 10)); + } + + @Test + void testIncorrectMultiplication() { + int[][] a = {{1, 2}, {3, 4}}; + int[][] b = {{5, 6}, {7, 8}}; + int[][] wrongC = {{20, 22}, {43, 51}}; + assertFalse(RandomizedMatrixMultiplicationVerification.verify(a, b, wrongC, 10)); + } + + @Test + void testLargeMatrix() { + int size = 100; + int[][] a = new int[size][size]; + int[][] b = new int[size][size]; + int[][] c = new int[size][size]; + + for (int i = 0; i < size; i++) { + a[i][i] = 1; + b[i][i] = 1; + c[i][i] = 1; + } + + assertTrue(RandomizedMatrixMultiplicationVerification.verify(a, b, c, 15)); + } +}