p14936.cpp

//
// Created by HEYX on 2026/1/15.
//

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

#define NAMESPACE_BEGIN(name) namespace name {
#define NAMESPACE_END }

NAMESPACE_BEGIN(Hyx)

#ifndef ONLINE_JUDGE
#include "debug_template.hpp"
#else
#define debug(...)
#define debugArr(...)
#endif // ONLINE_JUDGE

int n;
int a[100000];

int main() {
#ifndef ONLINE_JUDGE
  freopen("input.txt", "rb", stdin);
  // freopen("output.txt", "wb", stdout);
#endif // ONLINE_JUDGE
  int t;
  cin >> t;
  while (t--) {
    cin >> n;
    int xorsum = 0, mex = 0;
    for (int i = 1; i <= n; i++) cin >> a[i], xorsum ^= a[i];
    sort(a + 1, a + n + 1);
    for (int i = 1; i <= n; i++) mex += a[i] == mex;
    if (xorsum == mex) {
      cout << "0\n\n";
    } else {
      if (xorsum != 0) {
        cout << "1\n";
        cout << (xorsum^mex) << "\n";
      } else {
        cout << "2\n";
        cout << ((1 << 30) - 1) << " " << (((1 << 30) - 1) ^ mex) << "\n"; // 注意 << 是位运算符
      }
    }
  }
  return 0;
}

NAMESPACE_END

int main() {
#ifndef ONLINE_JUDGE
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
#endif // ONLINE_JUDGE
  return Hyx::main();
}