Contains Duplicates II

Description:

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.

Solution 1. Hash Map

Hashmap can easily store index and data together.

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