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 absolute difference between i and j is at most k.
Solution1：hashset
Time Complexity: O(N) Space Complexity: O(k)
Solution1 Code：
class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
Set<Integer> set = new HashSet<Integer>();
for(int i = 0; i < nums.length; i++) {
if(i > k) set.remove(nums[i - k - 1]);
if(!set.add(nums[i])) return true;
}
return false;
}
}
