Added 4 solutions

varunu28 · varunu28 · commit 219c0de830e3 · 2018-09-22T17:56:16.000-07:00
diff --git a/Easy/Design HashMap.java b/Easy/Design HashMap.java
@@ -0,0 +1,32 @@
+class MyHashMap {
+
+    /** Initialize your data structure here. */
+    int[] arr;
+    public MyHashMap() {
+        arr = new int[1000001];
+        Arrays.fill(arr, -1);
+    }
+
+    /** value will always be non-negative. */
+    public void put(int key, int value) {
+        arr[key] = value;
+    }
+
+    /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
+    public int get(int key) {
+        return arr[key];
+    }
+
+    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
+    public void remove(int key) {
+        arr[key] = -1;
+    }
+}
+
+/**
+ * Your MyHashMap object will be instantiated and called as such:
+ * MyHashMap obj = new MyHashMap();
+ * obj.put(key,value);
+ * int param_2 = obj.get(key);
+ * obj.remove(key);
+ */
diff --git a/Easy/Unique Morse Code Words.java b/Easy/Unique Morse Code Words.java
@@ -0,0 +1,18 @@
+class Solution {
+    public static int uniqueMorseRepresentations(String[] words) {
+        String[] codes = {".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
+        Set<String> set = new HashSet<>();
+
+        for (String word : words) {
+            StringBuilder sb = new StringBuilder();
+
+            for (char c : word.toCharArray()) {
+                sb.append(codes[c-'a']);
+            }
+
+            set.add(sb.toString());
+        }
+
+        return set.size();
+    }
+}
diff --git a/Medium/Summary Ranges.java b/Medium/Summary Ranges.java
@@ -0,0 +1,45 @@
+class Solution {
+    public List<String> summaryRanges(int[] nums) {
+        List<String> ranges = new ArrayList<>();
+
+        if (nums.length == 0) {
+            return ranges;
+        }
+
+        int count = 1;
+        int i = 0;
+        StringBuilder sb = new StringBuilder();
+        sb.append(nums[0]);
+        int n = nums.length-1;
+
+        while (i < n) {
+            if (nums[i+1] - nums[i] == 1) {
+                count++;
+            }
+            else {
+                if (count > 1) {
+                    sb.append("->").append(nums[i]);
+                    ranges.add(sb.toString());
+                    count = 1;
+                }
+                else {
+                    ranges.add(sb.toString());
+                }
+                sb = new StringBuilder();
+                sb.append(nums[i+1]);
+            }
+
+            i++;
+        }
+
+        if (count > 1) {
+            sb.append("->").append(nums[i]);
+            ranges.add(sb.toString());
+        }
+        else {
+            ranges.add(sb.toString());
+        }
+
+        return ranges;
+    }
+}
diff --git a/Medium/Top K Frequent Words.java b/Medium/Top K Frequent Words.java
@@ -0,0 +1,27 @@
+class Solution {
+    public List<String> topKFrequent(String[] words, int k) {
+
+        Map<String, Integer> map = new HashMap<>();
+
+        for (String word : words) {
+            map.put(word, map.getOrDefault(word, 0) + 1);
+        }
+
+        Queue<Map.Entry<String,Integer>> maxHeap =
+                        new PriorityQueue<>((o1,o2)->o1.getValue() == o2.getValue() ?
+                                                o1.getKey().compareTo(o2.getKey()) :
+                                                    o2.getValue()-o1.getValue());
+
+        for(Map.Entry<String,Integer> entry: map.entrySet()) {
+            maxHeap.offer(entry);
+        }
+
+        List<String> topKWords = new ArrayList<>();
+
+        while(topKWords.size() <k){
+            topKWords.add(maxHeap.poll().getKey());
+        }
+
+        return topKWords;
+    }
+}
