Skip to content

add MRU Implementation #2738

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 5 commits into from
Oct 28, 2021
Merged

add MRU Implementation #2738

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
ef6f729
add MRU Implementation
januslinhc Oct 25, 2021
49eed07
add MRU Implementation; Fixes: #2736
januslinhc Oct 25, 2021
7b29712
add MRU Implementation; Fixes: #2736
januslinhc Oct 25, 2021
89b201d
Merge branch 'master' into feature/MRU_Implementation
siriak Oct 28, 2021
589415d
Update directory
Oct 28, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 8 additions & 0 deletions DIRECTORY.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
* [IIRFilter](https://github.com/TheAlgorithms/Java/blob/master/AudioFilters/IIRFilter.java)

## Backtracking
* [KnightsTour](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/KnightsTour.java)
* [NQueens](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/NQueens.java)
* [PowerSum](https://github.com/TheAlgorithms/Java/blob/master/Backtracking/PowerSum.java)

Expand Down Expand Up @@ -48,6 +49,7 @@
* [CircularBuffer](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Buffers/CircularBuffer.java)
* Caches
* [LRUCache](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Caches/LRUCache.java)
* [MRUCache](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Caches/MRUCache.java)
* DisjointSets
* [DisjointSets](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/DisjointSets/DisjointSets.java)
* [Node](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/DisjointSets/Node.java)
Expand Down Expand Up @@ -82,6 +84,7 @@
* Lists
* [CircleLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CircleLinkedList.java)
* [CountSinglyLinkedListRecursion](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CountSinglyLinkedListRecursion.java)
* [CreateAndDetectLoop](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CreateAndDetectLoop.java)
* [CursorLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/CursorLinkedList.java)
* [DoublyLinkedList](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/DoublyLinkedList.java)
* [Merge K SortedLinkedlist](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Lists/Merge_K_SortedLinkedlist.java)
Expand Down Expand Up @@ -113,11 +116,14 @@
* [BSTRecursive](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/BSTRecursive.java)
* [BSTRecursiveGeneric](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/BSTRecursiveGeneric.java)
* [CeilInBinarySearchTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CeilInBinarySearchTree.java)
* [CreateBinaryTreeFromInorderPreorder](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CreateBinaryTreeFromInorderPreorder.java)
* [CreateBSTFromSortedArray](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/CreateBSTFromSortedArray.java)
* [FenwickTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/FenwickTree.java)
* [GenericTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/GenericTree.java)
* [LCA](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LCA.java)
* [LevelOrderTraversal](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LevelOrderTraversal.java)
* [LevelOrderTraversalQueue](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/LevelOrderTraversalQueue.java)
* [nearestRightKey](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/nearestRightKey.java)
* [PrintTopViewofTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/PrintTopViewofTree.java)
* [RedBlackBST](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/RedBlackBST.java)
* [SegmentTree](https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Trees/SegmentTree.java)
Expand Down Expand Up @@ -253,6 +259,7 @@
## Others
* [BestFit](https://github.com/TheAlgorithms/Java/blob/master/Others/BestFit.java)
* [BFPRT](https://github.com/TheAlgorithms/Java/blob/master/Others/BFPRT.java)
* [BoyerMoore](https://github.com/TheAlgorithms/Java/blob/master/Others/BoyerMoore.java)
* [BrianKernighanAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/Others/BrianKernighanAlgorithm.java)
* [CountChar](https://github.com/TheAlgorithms/Java/blob/master/Others/CountChar.java)
* [CountWords](https://github.com/TheAlgorithms/Java/blob/master/Others/CountWords.java)
Expand Down Expand Up @@ -317,6 +324,7 @@
* [SquareRootBinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/SquareRootBinarySearch.java)
* [TernarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/TernarySearch.java)
* [UnionFind](https://github.com/TheAlgorithms/Java/blob/master/Searches/UnionFind.java)
* [UpperBound](https://github.com/TheAlgorithms/Java/blob/master/Searches/UpperBound.java)

## Sorts
* [BitonicSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BitonicSort.java)
Expand Down
179 changes: 179 additions & 0 deletions DataStructures/Caches/MRUCache.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,179 @@
package DataStructures.Caches;

import java.util.HashMap;
import java.util.Map;

/**
* Most recently used (MRU)
* <p>
* In contrast to Least Recently Used (LRU), MRU discards the most recently used items first.
* https://en.wikipedia.org/wiki/Cache_replacement_policies#Most_recently_used_(MRU)
*
* @param <K> key type
* @param <V> value type
*/
public class MRUCache<K, V> {
private final Map<K, Entry<K, V>> data = new HashMap<>();
private Entry<K, V> head;
private Entry<K, V> tail;
private int cap;
private static final int DEFAULT_CAP = 100;

public MRUCache() {
setCapacity(DEFAULT_CAP);
}

private void setCapacity(int newCapacity) {
checkCapacity(newCapacity);
for (int i = data.size(); i > newCapacity; i--) {
Entry<K, V> evicted = evict();
data.remove(evicted.getKey());
}
this.cap = newCapacity;
}


private void checkCapacity(int capacity) {
if (capacity <= 0) {
throw new RuntimeException("capacity must greater than 0!");
}
}

private Entry<K, V> evict() {
if (head == null) {
throw new RuntimeException("cache cannot be empty!");
}
final Entry<K, V> evicted = this.tail;
tail = evicted.getPreEntry();
tail.setNextEntry(null);
evicted.setNextEntry(null);
return evicted;
}

public MRUCache(int cap) {
setCapacity(cap);
}

public V get(K key) {
if (!data.containsKey(key)) {
return null;
}
final Entry<K, V> entry = data.get(key);
moveEntryToLast(entry);
return entry.getValue();
}

public void put(K key, V value) {
if (data.containsKey(key)) {
final Entry<K, V> exitingEntry = data.get(key);
exitingEntry.setValue(value);
moveEntryToLast(exitingEntry);
return;
}
Entry<K, V> newEntry;
if (data.size() == cap) {
newEntry = evict();
data.remove(newEntry.getKey());
} else {
newEntry = new Entry<>();
}
newEntry.setKey(key);
newEntry.setValue(value);
addNewEntry(newEntry);
data.put(key, newEntry);
}

private void addNewEntry(Entry<K, V> newEntry) {
if (data.isEmpty()) {
head = newEntry;
tail = newEntry;
return;
}
tail.setNextEntry(newEntry);
newEntry.setPreEntry(tail);
newEntry.setNextEntry(null);
tail = newEntry;
}

private void moveEntryToLast(Entry<K, V> entry) {
if (tail == entry) {
return;
}
final Entry<K, V> preEntry = entry.getPreEntry();
final Entry<K, V> nextEntry = entry.getNextEntry();
if (preEntry != null) {
preEntry.setNextEntry(nextEntry);
}
if (nextEntry != null) {
nextEntry.setPreEntry(preEntry);
}
if (head == entry) {
head = nextEntry;
}
tail.setNextEntry(entry);
entry.setPreEntry(tail);
entry.setNextEntry(null);
tail = entry;
}

static final class Entry<I, J> {
private Entry<I, J> preEntry;
private Entry<I, J> nextEntry;
private I key;
private J value;

public Entry() {
}

public Entry(Entry<I, J> preEntry, Entry<I, J> nextEntry, I key, J value) {
this.preEntry = preEntry;
this.nextEntry = nextEntry;
this.key = key;
this.value = value;
}

public Entry<I, J> getPreEntry() {
return preEntry;
}

public void setPreEntry(Entry<I, J> preEntry) {
this.preEntry = preEntry;
}

public Entry<I, J> getNextEntry() {
return nextEntry;
}

public void setNextEntry(Entry<I, J> nextEntry) {
this.nextEntry = nextEntry;
}

public I getKey() {
return key;
}

public void setKey(I key) {
this.key = key;
}

public J getValue() {
return value;
}

public void setValue(J value) {
this.value = value;
}
}

public static void main(String[] args) {
final MRUCache<String, Integer> cache = new MRUCache<>(2);
cache.put("Key1", 1);
cache.put("Key2", 2);
cache.put("Key3", 3);
cache.put("Key4", 4);
System.out.println("getValue(Key1): " + cache.get("Key1"));
System.out.println("getValue(Key2): " + cache.get("Key2"));
System.out.println("getValue(Key3): " + cache.get("Key3"));
System.out.println("getValue(Key4): " + cache.get("Key4"));
}
}