Submission #1604487

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Source Code Expand

#include <iostream>
#include <algorithm>
using namespace std;

using ll = long long;

int main() {
  // 入力
  int N, M;
  cin >> N >> M;
  int x[M], y[M];
  for (int i = 0; i < M; i++) cin >> x[i] >> y[i];

  // 部分点解法
  // Nの順列を生成するたび、条件を満たすかM回確認すれば良い
  int n[N];
  for (int i = 0; i < N; i++) n[i] = i + 1;
  int ans = 0;
  do {
    bool flag = true;
    for (int i = 0; i < M; i++) {
      for (int j = 0; j < N; j++) {
        if (n[j] == y[i]) flag = false;
        else if (n[j] == x[i]) break;
      }
    }
    if (flag) ans++;
  } while (next_permutation(n, n + N));

  // 解答
  cout << ans << endl;

  return 0;
}

Submission Info

Judge Result