View Code of Problem 3929

#include<bits/stdc++.h> 
using namespace std;
long long visit[100005];
int main() {
	long long T;cin>>T;
	for(long long i=0;i<T;i++){
		long long n;cin>>n;
		memset(visit,0,sizeof(visit));
		vector<long long>v;
		for(long long j=0;j<n;j++){
			long long t;cin>>t;
			visit[t]++;
		}
		for(long long j=0;j<=100005;j++){
			if(visit[j]%2==1)
				v.push_back(j);
		}
		long long result=v[0];
		for(long long j=1;j<v.size();j++){
			result=result^v[j];
		}
		cout<<result<<endl;
		
		
	}
}