Problem p01187 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

#define REP(i, s, n) for (int i = s; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define inf (1 << 29)
#define all(n) (n).begin(), (n).end()
#define MAX_V 1100

using namespace std;

// follow
struct edge {
  int to, cap, rev;
  edge(int to = inf, int cap = inf, int rev = inf)
      : to(to), cap(cap), rev(rev) {}
};

vector<edge> G[MAX_V];
int level[MAX_V];
int iter[MAX_V];
bool used[MAX_V];

void init(int V) { rep(i, V) G[i].clear(); }

void add_edge(int from, int to, int cap) {
  G[from].push_back(edge(to, cap, G[to].size()));
  G[to].push_back(edge(from, 0, G[from].size() - 1));
}
/*
void bfs(int s)
{
  memset(level,-1,sizeof(level));
  queue<int> que;
  level[s] = 0;
  que.push(s);
  while(!que.empty())
    {
      int v = que.front(); que.pop();
      for(int i=0;i<G[v].size();i++)
        {
          edge &e = G[v][i];
          if(e.cap > 0 && level[e.to] < 0)
            {
              level[e.to] = level[v] + 1;
              que.push(e.to);
            }
        }
    }
}
*/
int dfs(int v, int t, int f) {
  if (v == t)
    return f;
  used[v] = true;
  for (int i = 0; i < G[v].size(); i++) {
    edge &e = G[v][i];
    if (e.cap > 0 && !used[e.to]) {
      int d = dfs(e.to, t, min(f, e.cap));
      if (d > 0) {
        e.cap -= d;
        G[e.to][e.rev].cap += d;
        return d;
      }
    }
  }
  return 0;
}

int max_flow(int s, int t) {
  int flow = 0;
  for (;;) {
    memset(used, 0, sizeof(used));
    int f = dfs(s, t, inf);
    if (f == 0) {
      return flow;
    }
    flow += f;
  }
}

//

int main() {
  int N;
  while (cin >> N, N) {
    int k, day, V, s, t;
    cin >> k;

    V = 2 + k + N;
    s = k + N;
    t = s + 1;
    init(V);
    map<int, int> days;
    vector<int> vday;
    rep(i, k) {
      cin >> day;
      vday.push_back(day);
      add_edge(s, i, 1);
    }
    sort(all(vday));
    rep(i, k) { days[vday[i]] = i; }

    int index = k;
    int K = k;

    rep(i, N) {
      cin >> k;
      rep(j, k) {
        cin >> day;
        if (days.find(day) != days.end()) {
          add_edge(days[day], K + i, 1);
        }
      }
      add_edge(K + i, t, 1);
    }

    cout << max_flow(s, t) << endl;
  }
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

#define REP(i, s, n) for (int i = s; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define inf (1 << 29)
#define all(n) (n).begin(), (n).end()
#define MAX_V 1100

using namespace std;

// follow
struct edge {
  int to, cap, rev;
  edge(int to = inf, int cap = inf, int rev = inf)
      : to(to), cap(cap), rev(rev) {}
};

vector<edge> G[MAX_V];
int level[MAX_V];
int iter[MAX_V];

void init(int V) { rep(i, V) G[i].clear(); }

void add_edge(int from, int to, int cap) {
  G[from].push_back(edge(to, cap, G[to].size()));
  G[to].push_back(edge(from, 0, G[from].size() - 1));
}

void bfs(int s) {
  memset(level, -1, sizeof(level));
  queue<int> que;
  level[s] = 0;
  que.push(s);
  while (!que.empty()) {
    int v = que.front();
    que.pop();
    for (int i = 0; i < G[v].size(); i++) {
      edge &e = G[v][i];
      if (e.cap > 0 && level[e.to] < 0) {
        level[e.to] = level[v] + 1;
        que.push(e.to);
      }
    }
  }
}

int dfs(int v, int t, int f) {
  if (v == t)
    return f;
  for (int &i = iter[v]; i < G[v].size(); i++) {
    edge &e = G[v][i];
    if (e.cap > 0 && level[v] < level[e.to]) {
      int d = dfs(e.to, t, min(f, e.cap));
      if (d > 0) {
        e.cap -= d;
        G[e.to][e.rev].cap += d;
        return d;
      }
    }
  }
  return 0;
}

int max_flow(int s, int t) {
  int flow = 0;
  for (;;) {
    bfs(s);
    if (level[t] < 0)
      return flow;
    memset(iter, 0, sizeof(iter));
    int f;
    while ((f = dfs(s, t, inf)) > 0) {
      flow += f;
    }
  }
}

//

int main() {
  int N;
  while (cin >> N, N) {
    int k, day, V, s, t;
    cin >> k;

    V = 2 + k + N;
    s = k + N;
    t = s + 1;
    init(V);
    map<int, int> days;
    vector<int> vday;
    rep(i, k) {
      cin >> day;
      vday.push_back(day);
      add_edge(s, i, 1);
    }
    sort(all(vday));
    rep(i, k) { days[vday[i]] = i; }

    int index = k;
    int K = k;

    rep(i, N) {
      cin >> k;
      rep(j, k) {
        cin >> day;
        if (days.find(day) != days.end()) {
          add_edge(days[day], K + i, 1);
        }
      }
      add_edge(K + i, t, 1);
    }

    cout << max_flow(s, t) << endl;
  }
  return 0;
}