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ID题目提交者结果用时内存语言文件大小提交时间测评时间
#153168#6858. Play on Treejrjyy#AC ✓114ms20796kbC++203.4kb2023-08-29 15:17:462023-08-29 15:17:47

Judging History

你现在查看的是最新测评结果

  • [2023-08-29 15:17:47]
  • 评测
  • 测评结果:AC
  • 用时:114ms
  • 内存:20796kb
  • [2023-08-29 15:17:46]
  • 提交

answer

/* l.cpp */
#include <bits/stdc++.h>

using i64 = long long;

template <typename T> constexpr T power(T a, i64 b) {
    T c{1}; for (; b; b /= 2, a *= a) if (b & 1) c *= a;
    return c;
}
template <int P> struct MInt {
    int x;
    constexpr MInt() : x{} {}
    constexpr MInt(i64 x_) : x{norm(x_ % getMod())} {}
    static int Mod;
    constexpr static int getMod() { return P > 0 ? P : Mod; }
    constexpr static void setMod(int Mod_) { Mod = Mod_; }
    constexpr int up(int x) const {
        if (x < 0) x += getMod();
        return x;
    }
    constexpr int down(int x) const {
        if (x >= getMod()) x -= getMod();
        return x;
    }
    constexpr int norm(int x) const {
        return up(down(x));
    }
    constexpr int val() const { return x; }
    explicit constexpr operator int() const { return x; }
    constexpr MInt operator-() const {
        MInt res; res.x = norm(getMod() - x); return res;
    }
    constexpr MInt inv() const {
        assert(x != 0);
        return power(*this, getMod() - 2);
    }
    constexpr MInt &operator+=(MInt rhs) & { return x = down(x + rhs.x), *this; }
    constexpr MInt &operator-=(MInt rhs) & { return x = up(x - rhs.x), *this; }
    constexpr MInt &operator*=(MInt rhs) & { return x = 1ll * x * rhs.x % getMod(), *this; }
    constexpr MInt &operator/=(MInt rhs) & { return *this *= rhs.inv(); }
    friend constexpr MInt operator+(MInt lhs, MInt rhs) { return lhs += rhs; }
    friend constexpr MInt operator-(MInt lhs, MInt rhs) { return lhs -= rhs; }
    friend constexpr MInt operator*(MInt lhs, MInt rhs) { return lhs *= rhs; }
    friend constexpr MInt operator/(MInt lhs, MInt rhs) { return lhs /= rhs; }
    friend constexpr bool operator==(MInt lhs, MInt rhs) { return lhs.val() == rhs.val(); }
    friend constexpr bool operator!=(MInt lhs, MInt rhs) { return lhs.val() != rhs.val(); }
    friend constexpr std::istream &operator>>(std::istream &is, MInt &a) {
        i64 x = 0; is >> x, a = MInt(x); return is;
    }
    friend constexpr std::ostream &operator<<(std::ostream &os, const MInt &a) {
        return os << a.val();
    }
};

template <int P> int MInt<P>::Mod = P;
template <> int MInt<0>::Mod = 1;
template <int V, int P> constexpr MInt<P> CInv = MInt<P>(V).inv();

constexpr int P = 1000000007;
using Z = MInt<P>;

void solve() {
    int n;
    std::cin >> n;

    std::vector<std::vector<int>> adj(n);
    for (int i = 0; i < n - 1; ++i) {
        int u, v;
        std::cin >> u >> v;
        --u, --v;
        adj[u].push_back(v), adj[v].push_back(u);
    }

    std::vector<int> f(n), g(n);
    auto dfs1 = [&](auto self, int u, int fa) -> void {
        for (auto v : adj[u]) if (v != fa) {
            self(self, v, u);
            f[u] ^= f[v] + 1;
        }
    };
    dfs1(dfs1, 0, -1);
    auto dfs2 = [&](auto self, int u, int fa) -> void {
        for (auto v : adj[u]) if (v != fa) {
            g[v] = f[u] ^ (f[v] + 1) ^ (g[u] + 1);
            self(self, v, u);
        }
    };
    g[0] = -1, dfs2(dfs2, 0, -1);

    Z ans = 0;
    for (int i = 0; i < n; ++i) {
        if ((f[i] ^ (g[i] + 1)) != 0) {
            ans += 1;
        }
    }

    std::cout << ans / n << '\n';
}

int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);

    int t;
    std::cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}

详细

Test #1:

score: 100
Accepted
time: 114ms
memory: 20796kb

input:

3
199999
144802 35753
35753 9646
9646 148183
9646 167003
9646 199831
9646 193968
9646 182279
9646 185547
9646 106896
9646 196577
9646 150627
9646 147736
9646 180949
9646 179482
9646 196999
9646 191636
9646 184859
9646 173080
9646 155500
9646 191682
9646 169619
9646 191285
9646 106525
9646 187324
964...

output:

256641286
960854812
384481201

result:

ok 3 lines