Problem p02651 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rep2(i, s, n) for (int i = (s); i < (n); ++i)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define eb emplace_back
#define vi vector<int>
#define vvi vector<vector<int>>
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vd vector<double>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vp vector<P>
using namespace std;
using ll = long long;
using P = pair<int, int>;
using LP = pair<ll, ll>;
template <class S, class T> istream &operator>>(istream &is, pair<S, T> &p) {
  return is >> p.first >> p.second;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
  return os << '{' << p.first << "," << p.second << '}';
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &t : v) {
    is >> t;
  }
  return is;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << '[';
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? ']' : ',');
  return os;
}
void Yes(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YES(bool b) { cout << (b ? "YES" : "NO") << endl; }
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const int inf = 1001001001;
const ll linf = 1001001001001001001;

void solve() {
  int n;
  cin >> n;
  vl a(n);
  cin >> a;
  string s;
  cin >> s;
  vl es;
  es.pb(0);
  rrep(i, n) {
    ll v = a[i];
    for (ll e : es)
      chmin(v, v ^ e);
    if (v) {
      if (s[i] == '1') {
        cout << 1 << '\\n';
        return;
      } else
        es.pb(v);
    }
  }
  cout << 0 << '\\n';
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int t;
  cin >> t;
  rep(i, t) solve();
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rep2(i, s, n) for (int i = (s); i < (n); ++i)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define eb emplace_back
#define vi vector<int>
#define vvi vector<vector<int>>
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vd vector<double>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vp vector<P>
using namespace std;
using ll = long long;
using P = pair<int, int>;
using LP = pair<ll, ll>;
template <class S, class T> istream &operator>>(istream &is, pair<S, T> &p) {
  return is >> p.first >> p.second;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
  return os << '{' << p.first << "," << p.second << '}';
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &t : v) {
    is >> t;
  }
  return is;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << '[';
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? ']' : ',');
  return os;
}
void Yes(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YES(bool b) { cout << (b ? "YES" : "NO") << endl; }
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const int inf = 1001001001;
const ll linf = 1001001001001001001;

map<pair<int, ll>, int> mp;
int n;
vl a;
string s;
int dfs(int t, ll x) {
  if (t == n)
    return (x == 0 ? 0 : 1);
  if (mp.count({t, x}))
    return mp[{t, x}];
  int ret;
  if (s[t] == '0') {
    ret = 1;
    if (!dfs(t + 1, x))
      ret = 0;
    if (!dfs(t + 1, x ^ a[t]))
      ret = 0;
  } else {
    ret = 0;
    if (dfs(t + 1, x))
      ret = 1;
    if (dfs(t + 1, x ^ a[t]))
      ret = 1;
  }
  return mp[{t, x}] = ret;
}

void solve() {
  cin >> n;
  a.clear();
  a.resize(n);
  cin >> a;
  cin >> s;
  mp.clear();
  cout << dfs(0, 0) << "\\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int t;
  cin >> t;
  rep(i, t) solve();
}