#471763 (C++17) No.827 総神童数

• 問題: No.827 総神童数
• ユーザー: Mister
• 提出日時: 2020-04-27 18:55:25
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 214 ms / 2,000 ms
• コード長: 3,586 bytes
• コンパイル時間: 1,277 ms
• コンパイル使用メモリ: 84,236 KB
• 最終ジャッジ日時: 2025-01-10 02:33:55
• ジャッジサーバーID （参考情報）: judge5 / judge5

ファイルパターン	結果
sample	AC * 3
other	AC * 36

ソースコード

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#include <iostream>
#include <vector>
#include <queue>
template <class Cost = int>
struct Edge {
    int src, dst;
    Cost cost;
    Edge(int src = -1, int dst = -1, Cost cost = 1)
        : src(src), dst(dst), cost(cost){};
    bool operator<(const Edge<Cost>& e) const { return this->cost < e.cost; }
    bool operator>(const Edge<Cost>& e) const { return this->cost > e.cost; }
};
template <class Cost = int>
struct Graph {
    std::vector<std::vector<Edge<Cost>>> graph;
    Graph(int n = 0) : graph(n) {}
    void span(bool direct, int src, int dst, Cost cost = 1) {
        graph[src].emplace_back(src, dst, cost);
        if (!direct) graph[dst].emplace_back(dst, src, cost);
    }
    std::vector<Edge<Cost>>& operator[](int v) { return graph[v]; }
    std::vector<Edge<Cost>> operator[](int v) const { return graph[v]; }
    int size() const { return graph.size(); }
};
template <int MOD>
struct ModInt {
    using lint = long long;
    int val;
    // constructor
    ModInt(lint v = 0) : val(v % MOD) {
        if (val < 0) val += MOD;
    };
    // unary operator
    ModInt operator+() const { return ModInt(val); }
    ModInt operator-() const { return ModInt(MOD - val); }
    ModInt inv() const { return this->pow(MOD - 2); }
    // arithmetic
    ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
    ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
    ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
    ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; }
    ModInt pow(lint n) const {
        auto x = ModInt(1);
        auto b = *this;
        while (n > 0) {
            if (n & 1) x *= b;
            n >>= 1;
            b *= b;
        }
        return x;
    }
    // compound assignment
    ModInt& operator+=(const ModInt& x) {
        if ((val += x.val) >= MOD) val -= MOD;
        return *this;
    }
    ModInt& operator-=(const ModInt& x) {
        if ((val -= x.val) < 0) val += MOD;
        return *this;
    }
    ModInt& operator*=(const ModInt& x) {
        val = lint(val) * x.val % MOD;
        return *this;
    }
    ModInt& operator/=(const ModInt& x) { return *this *= x.inv(); }
    // compare
    bool operator==(const ModInt& b) const { return val == b.val; }
    bool operator!=(const ModInt& b) const { return val != b.val; }
    // I/O
    friend std::istream& operator>>(std::istream& is, ModInt& x) noexcept { return is >> x.val; }
    friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept { return os << x.val; }
};
template <class Cost>
std::vector<int> bfs(const Graph<Cost>& graph, int s) {
    std::vector<Cost> dist(graph.size(), -1);
    dist[s] = 0;
    std::queue<int> que;
    que.push(s);
    while (!que.empty()) {
        int v = que.front();
        que.pop();
        for (const auto& e : graph[v]) {
            if (dist[e.dst] != -1) continue;
            dist[e.dst] = dist[v] + e.cost;
            que.push(e.dst);
        }
    }
    return dist;
}
constexpr int MOD = 1e9 + 7;
using mint = ModInt<MOD>;
void solve() {
    int n;
    std::cin >> n;
    Graph<> graph(n);
    for (int i = 0; i < n - 1; ++i) {
        int u, v;
        std::cin >> u >> v;
        graph.span(false, --u, --v);
    }
    mint ans = 0;
    auto ds = bfs(graph, 0);
    for (auto d : ds) ans += mint(d + 1).inv();
    for (int i = 1; i <= n; ++i) ans *= i;
    std::cout << ans << std::endl;
}
int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);
    solve();
    return 0;
}
 
 
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