L219. Contains Duplicate II

Problem:

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.

Example 1:

Input: nums = [1,2,3,1], k = 3
Output: true

Example 2:

Input: nums = [1,0,1,1], k = 1
Output: true

Example 3:

Input: nums = [1,2,3,1,2,3], k = 2
Output: false

Solution:

• hash map

public boolean containsNearbyDuplicate(int[] nums, int k) {
    if(nums == null || nums.length == 0) return false;
    Map<Integer, Integer> map = new HashMap<>();
    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;
}