View Code of Problem 3929

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
using namespace std;

int main(){
    int T,sum;
    cin>>T;
    while(T--){
        int n;
        cin>>n;
        sum=0;
        for(int i=0;i<n;i++){
            int x;
            cin>>x;
            if(i==0){
                sum+=x;
            }else{
                sum^=x;
            }
        }
        cout<<sum<<endl;
    }
    return 0;
}