Description

	#219	Contains Duplicate II	Medium
		Array	Top 150
Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= 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

Two-pointers

Runtime 2012ms

Memory 58.45MB

class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        if(k == 0) return false;
        int left = 0, right = 1;
        while(left < nums.length && right < nums.length) {
            //System.out.println(left + " " + right);
            if(nums[left] == nums[right])
                return true;
            if(right - left < k && right < nums.length -1)
                right ++;
            else {
                left ++;
                right = left + 1;
            }
        }
        return false;
    }
}

HashSet

Runtime 16ms

Memory 56.88MB

class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        if(k == 0 || nums.length < 2) return false;
        Set<Integer> set = new HashSet<>();
        for(int i = 0, j = 0; j < nums.length; j++) {
            if(!set.add(nums[j])) return true;
            if(set.size() >= k + 1)
                set.remove(nums[i++]);
        }
        return false;
    }
}