結果

問題 No.2337 Equidistant
ユーザー rniyarniya
提出日時 2023-06-02 22:43:25
言語 C++17
(gcc 12.3.0 + boost 1.83.0)
結果
AC  
実行時間 306 ms / 4,000 ms
コード長 7,269 bytes
コンパイル時間 2,639 ms
コンパイル使用メモリ 213,656 KB
実行使用メモリ 31,744 KB
最終ジャッジ日時 2024-06-09 00:27:43
合計ジャッジ時間 9,932 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge5
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テストケース

テストケース表示
入力 結果 実行時間
実行使用メモリ
testcase_00 AC 2 ms
5,248 KB
testcase_01 AC 2 ms
5,376 KB
testcase_02 AC 2 ms
5,376 KB
testcase_03 AC 2 ms
5,376 KB
testcase_04 AC 2 ms
5,376 KB
testcase_05 AC 2 ms
5,376 KB
testcase_06 AC 3 ms
5,376 KB
testcase_07 AC 4 ms
5,376 KB
testcase_08 AC 4 ms
5,376 KB
testcase_09 AC 3 ms
5,376 KB
testcase_10 AC 3 ms
5,376 KB
testcase_11 AC 278 ms
19,840 KB
testcase_12 AC 275 ms
19,840 KB
testcase_13 AC 281 ms
19,840 KB
testcase_14 AC 282 ms
19,712 KB
testcase_15 AC 279 ms
19,840 KB
testcase_16 AC 265 ms
19,840 KB
testcase_17 AC 280 ms
19,840 KB
testcase_18 AC 276 ms
19,840 KB
testcase_19 AC 276 ms
19,840 KB
testcase_20 AC 273 ms
19,840 KB
testcase_21 AC 233 ms
31,744 KB
testcase_22 AC 182 ms
20,388 KB
testcase_23 AC 239 ms
20,608 KB
testcase_24 AC 306 ms
27,776 KB
testcase_25 AC 266 ms
20,480 KB
testcase_26 AC 292 ms
27,648 KB
testcase_27 AC 256 ms
20,608 KB
testcase_28 AC 239 ms
20,480 KB
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ソースコード

diff # 

#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

struct HeavyLightDecomposition {
    std::vector<std::vector<int>> G;  // child of vertex v on heavy edge is G[v].front() if it is not parent of v
    int n, time;
    std::vector<int> par,  // parent of vertex v
        sub,               // size of subtree whose root is v
        dep,               // distance bitween root and vertex v
        head,              // vertex that is the nearest to root on heavy path of vertex v
        tree_id,           // id of tree vertex v belongs to
        vertex_id,         // id of vertex v (consecutive on heavy paths)
        vertex_id_inv;     // vertex_id_inv[vertex_id[v]] = v

    HeavyLightDecomposition(int n)
        : G(n),
          n(n),
          time(0),
          par(n, -1),
          sub(n),
          dep(n, 0),
          head(n),
          tree_id(n, -1),
          vertex_id(n, -1),
          vertex_id_inv(n) {}

    void add_edge(int u, int v) {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        G[u].emplace_back(v);
        G[v].emplace_back(u);
    }

    void build(std::vector<int> roots = {0}) {
        int tree_id_cur = 0;
        for (int& r : roots) {
            assert(0 <= r and r < n);
            dfs_sz(r);
            head[r] = r;
            dfs_hld(r, tree_id_cur++);
        }
        assert(time == n);
        for (int v = 0; v < n; v++) vertex_id_inv[vertex_id[v]] = v;
    }

    int idx(int v) const { return vertex_id[v]; }

    int la(int v, int k) const {
        assert(0 <= v and v < n);
        assert(0 <= k and k <= dep[v]);
        while (1) {
            int u = head[v];
            if (vertex_id[v] - k >= vertex_id[u]) return vertex_id_inv[vertex_id[v] - k];
            k -= vertex_id[v] - vertex_id[u] + 1;
            v = par[u];
        }
    }

    int lca(int u, int v) const {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        assert(tree_id[u] == tree_id[v]);
        for (;; v = par[head[v]]) {
            if (vertex_id[u] > vertex_id[v]) std::swap(u, v);
            if (head[u] == head[v]) return u;
        }
    }

    int jump(int s, int t, int i) const {
        assert(0 <= s and s < n);
        assert(0 <= t and t < n);
        assert(0 <= i);
        if (tree_id[s] != tree_id[t]) return -1;
        if (i == 0) return s;
        int p = lca(s, t), d = dep[s] + dep[t] - 2 * dep[p];
        if (d < i) return -1;
        if (dep[s] - dep[p] >= i) return la(s, i);
        return la(t, d - i);
    }

    int distance(int u, int v) const {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        assert(tree_id[u] == tree_id[v]);
        return dep[u] + dep[v] - 2 * dep[lca(u, v)];
    }

    template <typename F> void query_path(int u, int v, const F& f, bool vertex = false) const {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        assert(tree_id[u] == tree_id[v]);
        int p = lca(u, v);
        for (auto& e : ascend(u, p)) f(e.second, e.first + 1);
        if (vertex) f(vertex_id[p], vertex_id[p] + 1);
        for (auto& e : descend(p, v)) f(e.first, e.second + 1);
    }

    template <typename F> void query_path_noncommutative(int u, int v, const F& f, bool vertex = false) const {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        assert(tree_id[u] == tree_id[v]);
        int p = lca(u, v);
        for (auto& e : ascend(u, p)) f(e.first + 1, e.second);
        if (vertex) f(vertex_id[p], vertex_id[p] + 1);
        for (auto& e : descend(p, v)) f(e.first, e.second + 1);
    }

    template <typename F> void query_subtree(int u, const F& f, bool vertex = false) const {
        assert(0 <= u and u < n);
        f(vertex_id[u] + !vertex, vertex_id[u] + sub[u]);
    }

private:
    void dfs_sz(int v) {
        sub[v] = 1;
        if (!G[v].empty() and G[v].front() == par[v]) std::swap(G[v].front(), G[v].back());
        for (int& u : G[v]) {
            if (u == par[v]) continue;
            par[u] = v;
            dep[u] = dep[v] + 1;
            dfs_sz(u);
            sub[v] += sub[u];
            if (sub[u] > sub[G[v].front()]) std::swap(u, G[v].front());
        }
    }

    void dfs_hld(int v, int tree_id_cur) {
        vertex_id[v] = time++;
        tree_id[v] = tree_id_cur;
        for (int& u : G[v]) {
            if (u == par[v]) continue;
            head[u] = (u == G[v][0] ? head[v] : u);
            dfs_hld(u, tree_id_cur);
        }
    }

    std::vector<std::pair<int, int>> ascend(int u, int v) const {  // [u, v), v is ancestor of u
        std::vector<std::pair<int, int>> res;
        while (head[u] != head[v]) {
            res.emplace_back(vertex_id[u], vertex_id[head[u]]);
            u = par[head[u]];
        }
        if (u != v) res.emplace_back(vertex_id[u], vertex_id[v] + 1);
        return res;
    }

    std::vector<std::pair<int, int>> descend(int u, int v) const {  // (u, v], u is ancestor of v
        if (u == v) return {};
        if (head[u] == head[v]) return {{vertex_id[u] + 1, vertex_id[v]}};
        auto res = descend(u, par[head[v]]);
        res.emplace_back(vertex_id[head[v]], vertex_id[v]);
        return res;
    }
};

using namespace std;

typedef long long ll;
#define all(x) begin(x), end(x)
constexpr int INF = (1 << 30) - 1;
constexpr long long IINF = (1LL << 60) - 1;
constexpr int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

template <class T> istream& operator>>(istream& is, vector<T>& v) {
    for (auto& x : v) is >> x;
    return is;
}

template <class T> ostream& operator<<(ostream& os, const vector<T>& v) {
    auto sep = "";
    for (const auto& x : v) os << exchange(sep, " ") << x;
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) { return y < x and (x = forward<U>(y), true); }

template <class T, class U = T> bool chmax(T& x, U&& y) { return x < y and (x = forward<U>(y), true); }

template <class T> void mkuni(vector<T>& v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <class T> int lwb(const vector<T>& v, const T& x) { return lower_bound(begin(v), end(v), x) - begin(v); }

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N, Q;
    cin >> N >> Q;
    HeavyLightDecomposition G(N);
    for (int i = 0; i < N - 1; i++) {
        int A, B;
        cin >> A >> B;
        G.add_edge(--A, --B);
    }

    G.build();

    auto query = [&](int S, int T) -> int {
        if (G.dep[S] > G.dep[T]) swap(S, T);
        int d = G.distance(S, T);
        if (d & 1) return 0;
        int p = G.lca(S, T);
        if (p == S) {
            int u = G.jump(T, S, d / 2), v = G.jump(T, S, d / 2 - 1);
            return G.sub[u] - G.sub[v];
        } else if (G.distance(p, T) > d / 2) {
            int u = G.jump(T, S, d / 2), v = G.jump(T, S, d / 2 - 1);
            return G.sub[u] - G.sub[v];
        } else {
            assert(G.distance(p, T) == d / 2);
            int u = G.jump(T, p, d / 2 - 1), v = G.jump(S, p, d / 2 - 1);
            return N - G.sub[u] - G.sub[v];
        }
    };
    for (; Q--;) {
        int S, T;
        cin >> S >> T;
        cout << query(--S, --T) << '\n';
    }
    return 0;
}
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