design hit counter

Author: fishercoder1534

MEDIUM/src/medium/DesignHitCounter.java

@@ -0,0 +1,44 @@
+package medium;
+
+public class DesignHitCounter {
+
+}
+
+class HitCounter {
+    /**Looked at this post: https://discuss.leetcode.com/topic/48758/super-easy-design-o-1-hit-o-s-gethits-no-fancy-data-structure-is-needed,
+     * I added one more field k to make it more generic.*/
+    private int[] times;
+    private int[] hits;
+    private int k;
+    
+    /** Initialize your data structure here. */
+    public HitCounter() {
+        k = 300;
+        times = new int[k];
+        hits = new int[k];
+    }
+    
+    /** Record a hit.
+        @param timestamp - The current timestamp (in seconds granularity). */
+    public void hit(int timestamp) {
+        int index = timestamp % k;
+        if (times[index] != timestamp){
+            times[index] = timestamp;
+            hits[index] = 1;
+        } else {
+            hits[index]++;
+        }
+    }
+    
+    /** Return the number of hits in the past 5 minutes.
+        @param timestamp - The current timestamp (in seconds granularity). */
+    public int getHits(int timestamp) {
+        int total = 0;
+        for (int i = 0; i < k; i++){
+            if (timestamp - times[i] < k){
+                total += hits[i];
+            }
+        }
+        return total;
+    }
+}

README.md

@@ -34,6 +34,7 @@
 |370|[Range Addition](https://leetcode.com/problems/range-addition/)|[Solution](../../blob/master/MEDIUM/src/medium/RangeAddition.java)| O(n+k)|O(1) | Medium| 
 |366|[Find Leaves of Binary Tree](https://leetcode.com/problems/find-leaves-of-binary-tree/)|[Solution](../../blob/master/MEDIUM/src/medium/FindLeavesofBinaryTree.java)| O(n)|O(h) | Medium| DFS
 |364|[Nested List Weight Sum II](https://leetcode.com/problems/nested-list-weight-sum-ii/)|[Solution](../../blob/master/MEDIUM/src/medium/NestedListWeightSumII.java)| O(n)|O(h) | Medium| DFS
+|362|[Design Hit Counter](https://leetcode.com/problems/design-hit-counter/)|[Solution](../../blob/master/MEDIUM/src/medium/DesignHitCounter.java)| O(1) amortized|O(k) | Medium| Design
 |359|[Logger Rate Limiter](https://leetcode.com/problems/logger-rate-limiter/)|[Solution](../../blob/master/EASY/src/easy/LoggerRateLimiter.java)| amortized O(1)|O(k) | Easy| HashMap
 |350|[Intersection of Two Arrays II](https://leetcode.com/problems/intersection-of-two-arrays-ii/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArraysII.java)| O(m+n)|O((m+n)) could be optimized | Easy| HashMap, Binary Search
 |349|[Intersection of Two Arrays](https://leetcode.com/problems/intersection-of-two-arrays/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArrays.java)| O(m+n)|O(min(m,n)) | Easy| Two Pointers, Binary Search