219. Contains Duplicate II

• Difficulty: Easy

• Topics: Array, Hash Table

• Similar Questions:

  • Contains Duplicate

  • Contains Duplicate III

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.

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

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

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

Solutions:

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_map<int, int> valToIndex;
        for (int i = 0; i < nums.size(); ++i) {
            if (valToIndex.count(nums[i]) > 0 && i - valToIndex[nums[i]] <= k) {
                return true;
            }

            valToIndex[nums[i]] = i;
        }

        return false;
    }
};