1 public class Solution {
 2     public boolean containsNearbyDuplicate(int[] nums, int k) {
 3         if (nums.length == 0) return false;
 4         HashMap<Integer, Integer> h = new HashMap<Integer, Integer>();
 5         int index = 0;
 6 
 7         for (int i = 0; i < nums.length; i++) {
 8             if (h.containsKey(nums[i])) {
 9                 index = h.get(nums[i]);
10                 if (i - index <= k) return true;
11                 h.put(nums[i], i);
12             } else {
13                 h.put(nums[i], i);
14             }
15         }
16         return false;
17     }
18 }