public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {

        Map<Integer,Integer> map = new HashMap<Integer,Integer>();

        for(int i=0;i<nums.length;i++)
        {
            if(map.containsKey(nums[i]))
            {
                int pre = map.get(nums[i]);
                if(i-pre<=k) return true;
            }
            map.put(nums[i],i);
        }
        return false;
    }
}