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

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

// #define int long long
#define reps(i, s, n) for (int(i) = (s); (i) < (n); ++(i))
#define rep(i, n) reps(i, 0, n)
#define rept(i, n) rep(i, (n) + 1)
#define repst(i, s, n) reps(i, s, (n) + 1)
#define reprt(i, n, t) for (int(i) = (n); (i) >= (t); --(i))
#define repr(i, n) reprt(i, n, 0)
#define each(itr, v) for (auto &(itr) : (v))
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define tmax(x, y, z) max(x, max(y, z))
#define tmin(x, y, z) min(x, min(y, z))
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define ln '\\n'
#define bln(i, n) (((i) == (n)-1) ? '\\n' : ' ')
#define dbg(x) cout << #x " = " << (x) << ln << flush
#define dbga(x, n)                                                             \\
  {                                                                            \\
    cout << #x " : ";                                                          \\
    for (int(i) = 0; i < (n); ++i) {                                           \\
      cout << ((x)[i]) << (i == ((n)-1) ? '\\n' : ' ') << flush;                \\
    }                                                                          \\
  }
#define zero(a) memset(a, 0, sizeof(a))
#define unq(a) sort(all(a)), a.erase(unique(all(a)), a.end())

typedef long double ld;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<string> vst;
typedef vector<bool> vb;
typedef vector<ld> vld;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<vector<int>> mat;

const ll inf = (ll)1e9 + 10;
const ll linf = (ll)1e18 + 10;
const ll mod = (ll)(1e9 + 7);
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const int ddx[] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[] = {1, 1, 0, -1, -1, -1, 0, 1};
const double eps = 1e-10;

ll mop(ll a, ll b, ll m = mod) {
  ll r = 1;
  a %= m;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1)
      r = r * a % m;
    a = a * a % m;
  }
  return r;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }

struct oreno_initializer {
  oreno_initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
  }
} oreno_initializer;

// ━━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…
// .｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋
// ・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・

// n*m<=500よりmin(n,m)<=22
// n<=22なら全列挙、m<=22ならbitDP

int n, m, s[500][500];
string S[500];

int enu() {
  int res = 0;
  rep(b, 1 << n) {
    int t[500] = {};
    rep(i, n) if (b >> i & 1) rep(j, m) t[j] ^= s[i][j];
    if (accumulate(t, t + m, 0) == 0)
      chmax(res, __builtin_popcount(b));
  }
  return res;
}

int bit() {
  // dp[i][j]:
  // i番目のレシピまでで材料の偶奇の列がjとなるような選び方の中でレシピを最も多く使うもののレシピの個数
  int dp[2][1 << m];
  memset(dp, -1, sizeof(dp));
  dp[0][0] = 0;
  rep(I, n) {
    int i = I & 1, ii = 1 - i, k = 0;
    rep(j, m) if (s[I][j] == 1) k |= 1 << j;
    rep(j, 1 << m) if (dp[i][j] != -1) chmax(dp[ii][j], dp[i][j]),
        chmax(dp[ii][j ^ k], dp[i][j] + 1);
  }
  return dp[n & 1][0];
}

signed main() {
  while (1) {
    cin >> n >> m;
    if (n == 0)
      break;
    rep(i, n) {
      cin >> S[i];
      rep(j, m) s[i][j] = (S[i][j] == '1');
    }
    cout << (n <= m ? enu() : bit()) << ln;
  }
}


Error: TLE

Fixed submission:

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

// #define int long long
#define reps(i, s, n) for (int(i) = (s); (i) < (n); ++(i))
#define rep(i, n) reps(i, 0, n)
#define rept(i, n) rep(i, (n) + 1)
#define repst(i, s, n) reps(i, s, (n) + 1)
#define reprt(i, n, t) for (int(i) = (n); (i) >= (t); --(i))
#define repr(i, n) reprt(i, n, 0)
#define each(itr, v) for (auto &(itr) : (v))
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define tmax(x, y, z) max(x, max(y, z))
#define tmin(x, y, z) min(x, min(y, z))
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define ln '\\n'
#define bln(i, n) (((i) == (n)-1) ? '\\n' : ' ')
#define dbg(x) cout << #x " = " << (x) << ln << flush
#define dbga(x, n)                                                             \\
  {                                                                            \\
    cout << #x " : ";                                                          \\
    for (int(i) = 0; i < (n); ++i) {                                           \\
      cout << ((x)[i]) << (i == ((n)-1) ? '\\n' : ' ') << flush;                \\
    }                                                                          \\
  }
#define zero(a) memset(a, 0, sizeof(a))
#define unq(a) sort(all(a)), a.erase(unique(all(a)), a.end())

typedef long double ld;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<string> vst;
typedef vector<bool> vb;
typedef vector<ld> vld;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<vector<int>> mat;

const ll inf = (ll)1e9 + 10;
const ll linf = (ll)1e18 + 10;
const ll mod = (ll)(1e9 + 7);
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const int ddx[] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[] = {1, 1, 0, -1, -1, -1, 0, 1};
const double eps = 1e-10;

ll mop(ll a, ll b, ll m = mod) {
  ll r = 1;
  a %= m;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1)
      r = r * a % m;
    a = a * a % m;
  }
  return r;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }

struct oreno_initializer {
  oreno_initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
  }
} oreno_initializer;

// ━━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…
// .｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋
// ・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・

// n*m<=500よりmin(n,m)<=22
// n<=22なら全列挙、m<=22ならbitDP

int n, m;
string s[500];

int enu() {
  int res = 0;
  rep(b, 1 << n) {
    int t[500] = {};
    rep(i, n) if (b >> i & 1) rep(j, m) t[j] ^= (s[i][j] - '0');
    if (accumulate(t, t + m, 0) == 0)
      chmax(res, __builtin_popcount(b));
  }
  return res;
}

int bit() {
  // dp[i][j]:
  // i番目のレシピまでで材料の偶奇の列がjとなるような選び方の中でレシピを最も多く使うもののレシピの個数
  int dp[2][1 << m];
  memset(dp, -1, sizeof(dp));
  dp[0][0] = 0;
  rep(I, n) {
    int i = I & 1, ii = 1 - i, k = 0;
    rep(j, m) if (s[I][j] == '1') k |= 1 << j;
    rep(j, 1 << m) if (dp[i][j] != -1) chmax(dp[ii][j], dp[i][j]),
        chmax(dp[ii][j ^ k], dp[i][j] + 1);
  }
  return dp[n & 1][0];
}

signed main() {
  while (1) {
    cin >> n >> m;
    if (n == 0)
      break;
    rep(i, n) cin >> s[i];
    cout << (n <= m ? enu() : bit()) << ln;
  }
}