LeetCode——Contains Duplicate II

Description：

Given an array of integers and an integer k, find out whether there 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 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 j = map.get(nums[i]);
    			if(i-j<=k) {
    				return true;
    			}
    			else {
    				map.remove(nums[j]);
    				map.put(nums[i], i);
    			}
    		}
    		else {
    			map.put(nums[i], i);
    		}
    	}
    	return false;
    }
}