Missing Number In Array

Given an array of size N-1 such that it only contains distinct integers in the range of 1 to N. Find the missing element.

This has a simple approach we can sum all numbers from 1 to N then subtract from the sum of the array we will get the missing number.

#include <bits/stdc++.h>
using namespace std;
class Solution{
  public:
    int MissingNumber(vector<int>& array, int n) {
        // Your code goes here
        long long int sum=(n*(n+1))/2;
        long long sum2=0;
        for(auto x:array)
        {
            sum2+=x;
        }
        return (int)(sum-sum2);
    }
};

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n;
        cin >> n;

        vector<int> array(n - 1);
        for (int i = 0; i < n - 1; ++i) cin >> array[i];
        Solution obj;
        cout << obj.MissingNumber(array, n) << "\n";
    }
    return 0;
}