Contains Duplicate

Problem Statement - link #

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Examples #

Example 1:

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

Example 2:

Input: nums = [1,2,3,4]
Output: false

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

Constraints #

• 1 <= nums.length <= 10^5
• -10^9 <= nums[i] <= 10^9

Solution #

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> s;
        for(int i: nums)
            if(s.find(i)==s.end()) s.insert(i);
            else return true;
        return false;
    }
};