Submission #1564972

---

Source Code Expand

#include <bits/stdc++.h>

using namespace std;

int main()
{
  int N, M;
  cin >> N >> M;
  vector< int > g[50];
  int in[50] = {};
  for(int i = 0; i < M; i++) {
    int a, b;
    cin >> a >> b;
    --a, --b;
    g[b].push_back(a);
    ++in[a];
  }
  priority_queue< int > que;
  int sz = N;
  for(int i = 0; i < N; i++) {
    if(in[i] == 0) que.emplace(i);
  }

  while(!que.empty()) {
    int p = que.top();
    --sz;
    if(p == 0) {
      cout << sz + 1 << endl;
      return (0);
    }
    que.pop();
    for(auto &to : g[p]) {
      --in[to];
      if(in[to] == 0) que.emplace(to);
    }
  }
}

Submission Info

Judge Result