219. Contains Duplicate II

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

Approach 1: Hash table.

Code (Python)

Approach 1:

Code (C++)

Approach 1:

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

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_set<int> numsSet;
        for (int i = 0; i < nums.size(); ++i)
        {
            if (numsSet.find(nums[i]) != numsSet.end())
                return true;
            numsSet.insert(nums[i]);
            if (i - k >= 0)
                numsSet.erase(nums[i - k]);
        }
        return false;
    }
};