219. 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 absolute difference between i and j is at most k.

My solution:HashMap

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

Solution 2: 66666 in Discuss

public class Solution {    public boolean containsNearbyDuplicate(int[] nums, int k) {        Set<Integer> data=new HashSet<Integer>();        for(int i=0;i<nums.length;++i){            if(i>k)                data.remove(nums[i-k-1]);            if(!data.add(nums[i]))                return true;        }        return false;    }}