Contains Duplicateeasy

#include <iostream>
#include <vector>
#include <unordered_set>
using namespace std;

bool containsDuplicate(vector<int>& nums) {
    // TODO: return true if any value appears more than once
    return false;
}

int main() {
    vector<int> a = {1, 2, 3, 1};
    vector<int> b = {1, 2, 3, 4};
    cout << boolalpha << containsDuplicate(a) << endl; // true
    cout << containsDuplicate(b) << endl;               // false
    return 0;
}