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219. Contains Duplicate II (Easy)

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

Related Topics:
Array, Hash Table

Similar Questions:

• Contains Duplicate (Easy)
• Contains Duplicate III (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/contains-duplicate-ii/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(N)
class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& A, int k) {
        unordered_map<int, int> m;
        for (int i = 0; i < A.size(); ++i) {
            if (m.count(A[i]) && i - m[A[i]] <= k) return true;
            m[A[i]] = i;
        }
        return false;
    }
};