003_missing_number_in_array

#include<iostream>
using namespace std;
class Solution{
  public:
    int MissingNumber(vector<int>& array, int n) {
         int ret = 0;
    for (int i = 0; i < n-1; i++)
      {
        ret += array[i];
         }
    return ((n * (n + 1)) / 2) - ret;
   }
};
//{ Driver Code Starts.

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;
}