Contains Duplicate II

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 jis at most k.

 

public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        HashSet<Integer> hashSet = new HashSet<>();
        int i = 0;
        int j = 0;
        for (; i < nums.length; i++) {
			if (i - j > k) {
				hashSet.remove(nums[j]);
				j++;
			}
			if (hashSet.contains(nums[i])) {
				return true;
			} 
			hashSet.add(nums[i]);
		}
		return false;
    }
}