結果

問題 No.1833 Subway Planning
ユーザー ei1333333
提出日時 2022-02-04 21:57:36
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 874 ms / 4,000 ms
コード長 4,741 bytes
コンパイル時間 2,431 ms
コンパイル使用メモリ 204,272 KB
最終ジャッジ日時 2025-01-27 19:07:08
ジャッジサーバーID
（参考情報） 		judge3 / judge1
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ファイルパターン 結果
sample AC * 3
other AC * 23
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
using int64 = long long;
// const int mod = 1e9 + 7;
const int mod = 998244353;
const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;
struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;
template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}
template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}
template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}
template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in: v) is >> in;
  return is;
}
template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}
template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}
template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}
template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e: t) fill_v(e, v);
}
template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}
  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};
template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}
/**
 * @brief Graph Template(グラフテンプレート)
 */
template< typename T = int >
struct Edge {
  int from, to;
  T cost;
  int idx;
  Edge() = default;
  Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {}
  operator int() const { return to; }
};
template< typename T = int >
struct Graph {
  vector< vector< Edge< T > > > g;
  int es;
  Graph() = default;
  explicit Graph(int n) : g(n), es(0) {}
  size_t size() const {
    return g.size();
  }
  void add_directed_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es++);
  }
  void add_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es);
    g[to].emplace_back(to, from, cost, es++);
  }
  void read(int M, int padding = -1, bool weighted = false, bool directed = false) {
    for(int i = 0; i < M; i++) {
      int a, b;
      cin >> a >> b;
      a += padding;
      b += padding;
      T c = T(1);
      if(weighted) cin >> c;
      if(directed) add_directed_edge(a, b, c);
      else add_edge(a, b, c);
    }
  }
  inline vector< Edge< T > > &operator[](const int &k) {
    return g[k];
  }
  inline const vector< Edge< T > > &operator[](const int &k) const {
    return g[k];
  }
};
template< typename T = int >
using Edges = vector< Edge< T > >;
int main() {
  int N;
  cin >> N;
  vector< int > A(N), B(N), C(N);
  Graph<> g(N);
  for(int i = 1; i < N; i++) {
    cin >> A[i] >> B[i] >> C[i];
    --A[i], --B[i];
    g.add_edge(A[i], B[i], C[i]);
  }
  auto check = [&](int d) -> bool {
    int need = 0;
    for(int i = 1; i < N; i++) {
      need += C[i] > d;
    }
    for(int i = 1; i < N; i++) {
      if(C[i] > d) {
        auto dfs = MFP([&](auto dfs, int idx, int par) -> tuple< int, int, int > {
          int ret = 0, low = inf, high = -inf;
          int uku = 1 + (par == -1);
          for(auto to: g[idx]) {
            if(to == par) continue;
            auto[a, b, c] = dfs(to, idx);
            c += to.cost > d;
            if(c > 0) {
              ret += c;
              chmin(low, to.cost);
              chmax(high, to.cost);
              chmin(low, a);
              chmax(high, b);
              --uku;
              if(uku == 0) break;
            }
          }
          return {low, high, ret};
        });
        auto[low, high, ret] = dfs(A[i], -1);
        if(need != ret) {
          return false;
        }
        if(high - low > d) {
          return false;
        }
        return true;
      }
    }
    return true;
  };
  int ok = inf, ng = -1;
  while(ok - ng > 1) {
    int mid = (ok + ng) / 2;
    if(check(mid)) ok = mid;
    else ng = mid;
  }
  cout << ok << "\n";
}
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