contains duplicate II

fishercoder1534 · fishercoder1534 · commit 02919543b0d0 · 2016-08-06T15:54:55.000-07:00
diff --git a/EASY/src/easy/ContainsDuplicateII.java b/EASY/src/easy/ContainsDuplicateII.java
@@ -0,0 +1,26 @@
+package easy;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**219. Contains Duplicate II  QuestionEditorial Solution  My Submissions
+Total Accepted: 69920
+Total Submissions: 228733
+Difficulty: Easy
+Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.*/
+public class ContainsDuplicateII {
+    //pretty straightforward, use a hashmap, key is the number itself, value is the last index that this value appeared in the array
+    //we can keep updating the value as we move forward, since if the current index minus the last index cannot be smaller than k, then
+    //the later indices won't even do either. So, we only need to keep one index in the value of the HashMap. Cheers!
+    public boolean containsNearbyDuplicate(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap();
+        for(int i = 0; i < nums.length; i++){
+            if(map.containsKey(nums[i])) {
+                if(i - map.get(nums[i]) <= k) return true;
+                else map.put(nums[i], i);
+            }
+            else map.put(nums[i], i);
+        }
+        return false;
+    }
+}
