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.

• Time: O(n)
• Space: O(1)

public boolean containsNearbyDuplicate(int[] nums, int k) {
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < nums.length; i++) {
        Integer pre = map.get(nums[i]);
        if (pre != null && (i - pre) <= k) {
            return true;
        }
        map.put(nums[i], i);
    }
    return false;
}