Problem p01104 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
typedef double ld;
typedef complex<ld> Point;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop                                                                   \\
  char nyaa;                                                                   \\
  cin >> nyaa;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
const ld eps = 1e-4;
const ld pi = acos(-1.0);
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
typedef vector<int> vec;

int n, m;
void solve() {
  vector<vector<bool>> b(n);
  rep(i, n) {
    b[i].resize(m, false);
    rep(j, m) {
      char t;
      cin >> t;
      b[i][j] = (t == '1');
    }
  }
  // cout << "ans is ";
  if (n <= 21) {
    int ans = 0;
    rep(i, (1 << n)) {
      vector<int> c(m, 0);
      int cnt = 0;
      rep(j, n) {
        if (i & (1 << j)) {
          cnt++;
          rep(k, m) if (b[j][k]) c[k] ^= 1;
        }
      }
      bool f = true;
      rep(k, m) if (c[k]) f = false;
      if (f)
        ans = max(ans, cnt);
    }
    cout << ans << endl;
  } else {
    vector<int> dp(1 << m, -mod), cop(1 << m);
    dp[0] = 0;
    rep(i, n) {
      fill(cop.begin(), cop.end(), -mod);
      int z = 0;
      rep(k, m) if (b[i][k]) z += (1 << k);
      rep(j, (1 << m)) { cop[j ^ z] = max(cop[j ^ z], dp[j] + 1); }
      rep(j, (1 << m)) { dp[j] = max(dp[j], cop[j]); }
    }
    cout << dp[0] << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(10);
  while (cin >> n >> m, n)
    solve();
  // solve();
  // stop
  return 0;
}


Error: TLE

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
typedef double ld;
typedef complex<ld> Point;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop                                                                   \\
  char nyaa;                                                                   \\
  cin >> nyaa;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
const ld eps = 1e-4;
const ld pi = acos(-1.0);
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
typedef vector<int> vec;

int n, m;
void solve() {
  vector<vector<bool>> b(n);
  rep(i, n) {
    b[i].resize(m, false);
    rep(j, m) {
      char t;
      cin >> t;
      b[i][j] = (t == '1');
    }
  }
  // cout << "ans is ";
  if (n <= 22) {
    int ans = 0;
    rep(i, (1 << n)) {
      vector<int> c(m, 0);
      int cnt = 0;
      rep(j, n) {
        if (i & (1 << j)) {
          cnt++;
          rep(k, m) if (b[j][k]) c[k] ^= 1;
        }
      }
      bool f = true;
      rep(k, m) if (c[k]) f = false;
      if (f)
        ans = max(ans, cnt);
    }
    cout << ans << endl;
  } else {
    vector<int> dp(1 << m, -mod), cop(1 << m);
    dp[0] = 0;
    rep(i, n) {
      fill(cop.begin(), cop.end(), -mod);
      int z = 0;
      rep(k, m) if (b[i][k]) z += (1 << k);
      rep(j, (1 << m)) { cop[j ^ z] = max(cop[j ^ z], dp[j] + 1); }
      rep(j, (1 << m)) { dp[j] = max(dp[j], cop[j]); }
    }
    cout << dp[0] << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(10);
  while (cin >> n >> m, n)
    solve();
  // solve();
  // stop
  return 0;
}