#1030373 (C++17) No.2980 Planar Tree 2

• 問題: No.2980 Planar Tree 2
• ユーザー: tnakao0123
• 提出日時: 2024-12-07 17:57:58
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 168 ms / 2,000 ms
• コード長: 2,113 bytes
• コンパイル時間: 690 ms
• コンパイル使用メモリ: 57,164 KB
• 最終ジャッジ日時: 2025-02-26 11:28:37
• ジャッジサーバーID （参考情報）: judge3 / judge3

ファイルパターン	結果
other	AC * 30

コンパイルメッセージ

main.cpp: In function ‘int main()’:
main.cpp:70:8: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   70 |   scanf("%d", &n);
      |   ~~~~~^~~~~~~~~~
main.cpp:73:10: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   73 |     scanf("%d%d", &u, &v);
      |     ~~~~~^~~~~~~~~~~~~~~~

ソースコード

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/* -*- coding: utf-8 -*-
 *
 * 2980.cc:  No.2980 Planar Tree 2 - yukicoder
 */
#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
/* constant */
const int MAX_N = 200000;
const int MOD = 998244353;
/* typedef */
using vi = vector<int>;
template<const int MOD>
struct MI {
  int v;
  MI(): v() {}
  MI(int _v): v(_v % MOD) { if (v < 0) v += MOD; }
  MI(long long _v): v(_v % MOD) { if (v < 0) v += MOD; }
  explicit operator int() const { return v; }
  
  MI operator+(const MI m) const { return MI(v + m.v); }
  MI operator-(const MI m) const { return MI(v + MOD - m.v); }
  MI operator*(const MI m) const { return MI((long long)v * m.v); }
  MI &operator+=(const MI m) { return (*this = *this + m); }
  MI &operator-=(const MI m) { return (*this = *this - m); }
  MI &operator*=(const MI m) { return (*this = *this * m); }
  bool operator==(const MI m) const { return v == m.v; }
  bool operator!=(const MI m) const { return v != m.v; }
  MI pow(int n) const {  // a^n % MOD
    MI pm = 1, a = *this;
    while (n > 0) {
      if (n & 1) pm *= a;
      a *= a;
      n >>= 1;
    }
    return pm;
  }
  MI inv() const { return pow(MOD - 2); }
  MI operator/(const MI m) const { return *this * m.inv(); }
  MI &operator/=(const MI m) { return (*this = *this / m); }
};
using mi = MI<MOD>;
/* global variables */
vi nbrs[MAX_N];
mi fs[MAX_N + 1], dp[MAX_N];
int ps[MAX_N], cis[MAX_N];
/* subroutines */
/* main */
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i < n; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    nbrs[u].push_back(v);
    nbrs[v].push_back(u);
  }
  fs[0] = 1;
  for (int i = 1; i <= n; i++) fs[i] = fs[i - 1] * i;
  fill(dp, dp + n, 1);
  ps[0] = -1;
  for (int u = 0; u >= 0;) {
    auto &nbru = nbrs[u];
    int up = ps[u];
    if (cis[u] < nbru.size()) {
      int v = nbru[cis[u]++];
      if (v != up) {
    ps[v] = u;
    u = v;
      }
    }
    else {
      dp[u] *= fs[nbru.size()];
      if (up >= 0) dp[up] *= dp[u];
      u = up;
    }
  }
  mi x = dp[0] / fs[n - 1];
  printf("%d\n", (int)x);
  
  return 0;
}
 
 
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