Leetcode: 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 j is at most k.

Code (Java):

public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        if (nums == null || nums.length <= 1 || k <= 0) {
            return false;
        }
        
        Map<Integer, Integer> map = new HashMap<>();
        
        for (int i = 0; i < nums.length; i++) {
            if (map.containsKey(nums[i])) {
                int preIndex = map.get(nums[i]);
                if (i - preIndex <= k) {
                    return true;
                } else {
                    map.put(nums[i], i);
                }
            } else {
                map.put(nums[i], i);
            }
        }
        
        return false;
    }
}

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