Problem p02914 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define INF (int)(1123456789)
#define LINF (long long int)(112345678901234567)
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))
#define all(v) v.begin(), v.end()

const int N = (int)3e5;

ll mpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = mpow(a, b / 2);
    return memo * memo % MOD;
  } else
    return mpow(a, b - 1) * a % MOD;
}
ll lpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = lpow(a, b / 2);
    return memo * memo;
  } else
    return lpow(a, b - 1) * a;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
vector<ll> kaijo_memo;
ll kaijo(ll n) {
  if (kaijo_memo.size() > n)
    return kaijo_memo[n];
  if (kaijo_memo.size() == 0)
    kaijo_memo.push_back(1);
  while (kaijo_memo.size() <= n)
    kaijo_memo.push_back(kaijo_memo[kaijo_memo.size() - 1] * kaijo_memo.size() %
                         MOD);
  return kaijo_memo[n];
}
ll nCr(ll n, ll r) {
  if (n < r || r < 0)
    return 0;
  ll ret = 1;
  ret *= kaijo(n);
  ret %= MOD;
  ret *= mpow(kaijo(r), MOD - 2);
  ret %= MOD;
  ret *= mpow(kaijo(n - r), MOD - 2);
  ret %= MOD;
  return ret;
}

int main(void) {
  int n;
  cin >> n;
  vector<vector<int>> A;
  rep(i, n) {
    ll a;
    cin >> a;
    A.push_back(vector<int>());
    rep(j, 60) {
      A[i].push_back(a % 2);
      a /= 2;
    }
    reverse(all(A[i]));
  }
  ll ans = 0;
  rep(c, 60) {
    int count = 0;
    rep(i, n) { count += A[i][c]; }
    if (count % 2 == 1) {
      ans += lpow((ll)2, 60 - c - 1);
      rep(i, n) { A[i][c] = 0; }
    }
  }
  vector<bool> kitei;
  rep(i, n) { kitei.push_back(false); }
  rep(c, 60) {
    int br = 0;
    while (br < n && (A[br][c] == 0 || kitei[br])) {
      br++;
    }
    if (br == n) {
      continue;
    }
    kitei[br] = true;
    rep(r, n) {
      if (br == r)
        continue;
      if (A[r][c] == 1) {
        rep(j, 60) { A[r][j] ^= A[br][j]; }
      }
    }
  }
  rep(i, n) {
    rep(j, 60) { cerr << A[i][j]; }
    cerr << endl;
  }

  vector<ll> count;

  rep(i, 60) { count.push_back(0); }
  rep(c, 60) {
    if (count[c] > 0) {
      if (count[c] % 2 == 1) {
        ans += lpow((ll)2, 60 - c);
      }
      continue;
    }
    int r = 0;
    while (r < n && A[r][c] == 0) {
      r++;
    }
    if (r == n)
      continue;

    rep(j, 60) { count[j] += A[r][j]; }
    ans += lpow((ll)2, 60 - c);
  }
  cout << ans << endl;
  return 0;
}


Fixed submission:
#include <algorithm>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define INF (int)(1123456789)
#define LINF (long long int)(112345678901234567)
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))
#define all(v) v.begin(), v.end()

const int N = (int)3e5;

ll mpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = mpow(a, b / 2);
    return memo * memo % MOD;
  } else
    return mpow(a, b - 1) * a % MOD;
}
ll lpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = lpow(a, b / 2);
    return memo * memo;
  } else
    return lpow(a, b - 1) * a;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
vector<ll> kaijo_memo;
ll kaijo(ll n) {
  if (kaijo_memo.size() > n)
    return kaijo_memo[n];
  if (kaijo_memo.size() == 0)
    kaijo_memo.push_back(1);
  while (kaijo_memo.size() <= n)
    kaijo_memo.push_back(kaijo_memo[kaijo_memo.size() - 1] * kaijo_memo.size() %
                         MOD);
  return kaijo_memo[n];
}
ll nCr(ll n, ll r) {
  if (n < r || r < 0)
    return 0;
  ll ret = 1;
  ret *= kaijo(n);
  ret %= MOD;
  ret *= mpow(kaijo(r), MOD - 2);
  ret %= MOD;
  ret *= mpow(kaijo(n - r), MOD - 2);
  ret %= MOD;
  return ret;
}

int main(void) {
  int n;
  cin >> n;
  vector<vector<int>> A;
  rep(i, n) {
    ll a;
    cin >> a;
    A.push_back(vector<int>());
    rep(j, 60) {
      A[i].push_back(a % 2);
      a /= 2;
    }
    reverse(all(A[i]));
  }
  ll ans = 0;
  rep(c, 60) {
    int count = 0;
    rep(i, n) { count += A[i][c]; }
    if (count % 2 == 1) {
      ans += lpow((ll)2, 60 - c - 1);
      rep(i, n) { A[i][c] = 0; }
    }
  }
  vector<bool> kitei;
  rep(i, n) { kitei.push_back(false); }
  rep(c, 60) {
    int br = 0;
    while (br < n && (A[br][c] == 0 || kitei[br])) {
      br++;
    }
    if (br == n) {
      continue;
    }
    kitei[br] = true;
    rep(r, n) {
      if (br == r)
        continue;
      if (A[r][c] == 1) {
        rep(j, 60) { A[r][j] ^= A[br][j]; }
      }
    }
  }
  /*rep(i,n){
          rep(j,60){
                  cerr<<A[i][j];
          }
          cerr<<endl;
  }*/

  vector<ll> count;

  rep(i, 60) { count.push_back(0); }
  rep(c, 60) {
    if (count[c] > 0) {
      if (count[c] % 2 == 1) {
        ans += lpow((ll)2, 60 - c);
      }
      continue;
    }
    int r = 0;
    while (r < n && A[r][c] == 0) {
      r++;
    }
    if (r == n)
      continue;

    rep(j, 60) { count[j] += A[r][j]; }
    ans += lpow((ll)2, 60 - c);
  }
  cout << ans << endl;
  return 0;
}