Problem p03931 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#define X first
#define Y second
#define pb push_back
#define rep(X, Y) for (int(X) = 0; (X) < (Y); ++(X))
#define reps(X, S, Y) for (int(X) = S; (X) < (Y); ++(X))
#define rrep(X, Y) for (int(X) = (Y)-1; (X) >= 0; --(X))
#define repe(X, Y) for ((X) = 0; (X) < (Y); ++(X))
#define peat(X, Y) for (; (X) < (Y); ++(X))
#define all(X) (X).begin(), (X).end()
#define rall(X) (X).rbegin(), (X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)), (X).end())

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
template <class T> using vv = vector<vector<T>>;
template <class T> ostream &operator<<(ostream &os, const vector<T> &t) {
  os << "{";
  rep(i, t.size()) { os << t[i] << ","; }
  os << "}" << endl;
  return os;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &t) {
  return os << "(" << t.first << "," << t.second << ")";
}
template <class T> inline bool MX(T &l, const T &r) {
  return l < r ? l = r, 1 : 0;
}
template <class T> inline bool MN(T &l, const T &r) {
  return l > r ? l = r, 1 : 0;
}
const ll MOD = 1e9 + 7;

ll dp[100][333][333];

int main() {
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(0);
  int n, t;
  cin >> n >> t;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  dp[0][0][0] = 1;
  rep(i, n) rep(j, n + 1) rep(k, 256) {
    (dp[i + 1][j + 1][k ^ a[i]] += dp[i][j][k]) %= MOD;
    (dp[i + 1][j][k] += dp[i][j][k]) %= MOD;
  }
  // rep(k,n+1){rep(i,n+1){rep(j,16)
  // cout<<dp[k][i][j]<<",";cout<<endl;}cout<<endl;}
  ll re = (t == 0), f = 1;
  reps(i, 1, n + 1) {
    (f *= i) %= MOD;
    // cout<<dp[n][i][t]<<endl;
    (re += dp[n][i][t] * f % MOD) %= MOD;
  }
  cout << re << endl;
  return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#define X first
#define Y second
#define pb push_back
#define rep(X, Y) for (int(X) = 0; (X) < (Y); ++(X))
#define reps(X, S, Y) for (int(X) = S; (X) < (Y); ++(X))
#define rrep(X, Y) for (int(X) = (Y)-1; (X) >= 0; --(X))
#define repe(X, Y) for ((X) = 0; (X) < (Y); ++(X))
#define peat(X, Y) for (; (X) < (Y); ++(X))
#define all(X) (X).begin(), (X).end()
#define rall(X) (X).rbegin(), (X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)), (X).end())

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
template <class T> using vv = vector<vector<T>>;
template <class T> ostream &operator<<(ostream &os, const vector<T> &t) {
  os << "{";
  rep(i, t.size()) { os << t[i] << ","; }
  os << "}" << endl;
  return os;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &t) {
  return os << "(" << t.first << "," << t.second << ")";
}
template <class T> inline bool MX(T &l, const T &r) {
  return l < r ? l = r, 1 : 0;
}
template <class T> inline bool MN(T &l, const T &r) {
  return l > r ? l = r, 1 : 0;
}
const ll MOD = 1e9 + 7;

ll dp[111][111][333];

int main() {
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(0);
  int n, t;
  cin >> n >> t;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  dp[0][0][0] = 1;
  rep(i, n) rep(j, n + 1) rep(k, 256) {
    (dp[i + 1][j + 1][k ^ a[i]] += dp[i][j][k]) %= MOD;
    (dp[i + 1][j][k] += dp[i][j][k]) %= MOD;
  }
  // rep(k,n+1){rep(i,n+1){rep(j,16)
  // cout<<dp[k][i][j]<<",";cout<<endl;}cout<<endl;}
  ll re = (t == 0), f = 1;
  reps(i, 1, n + 1) {
    (f *= i) %= MOD;
    // cout<<dp[n][i][t]<<endl;
    (re += dp[n][i][t] * f % MOD) %= MOD;
  }
  cout << re << endl;
  return 0;
}