Contains Duplicate

Problem

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.

Solution Approach

Expected Time Complexity: $O(n)$

Click - to see solution code

C++

class Solution {
   public:
    bool containsDuplicate(vector<int>& nums) {
        set<int> st(nums.begin(), nums.end());
        return st.size() != nums.size();
    }
};