結果

問題 No.2337 Equidistant
ユーザー ForestedForested
提出日時 2023-06-02 21:35:41
言語 C++17(gcc12)
(gcc 12.3.0 + boost 1.87.0)
結果
AC  
実行時間 230 ms / 4,000 ms
コード長 8,438 bytes
コンパイル時間 1,577 ms
コンパイル使用メモリ 140,388 KB
実行使用メモリ 32,500 KB
最終ジャッジ日時 2024-12-28 16:43:25
合計ジャッジ時間 7,675 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 1
other AC * 28
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 # 

#ifndef LOCAL
#define FAST_IO
#endif

// ============
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define OVERRIDE(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, m, n) for (i32 i = (i32)(m); i < (i32)(n); ++i)
#define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER(i, n) for (i32 i = (i32)(n) - 1; i >= 0; --i)
#define ALL(x) begin(x), end(x)

using namespace std;

using u32 = unsigned int;
using u64 = unsigned long long;
using i32 = signed int;
using i64 = signed long long;
using f64 = double;
using f80 = long double;

template <typename T>
using Vec = vector<T>;

template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}

#ifdef INT128

using u128 = __uint128_t;
using i128 = __int128_t;

istream &operator>>(istream &is, i128 &x) {
    i64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, i128 x) {
    os << (i64)x;
    return os;
}
istream &operator>>(istream &is, u128 &x) {
    u64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, u128 x) {
    os << (u64)x;
    return os;
}

#endif

[[maybe_unused]] constexpr i32 INF = 1000000100;
[[maybe_unused]] constexpr i64 INF64 = 3000000000000000100;
struct SetUpIO {
    SetUpIO() {
#ifdef FAST_IO
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
#endif
        cout << fixed << setprecision(15);
    }
} set_up_io;
// ============

#ifdef DEBUGF
#else
#define DBG(x) (void)0
#endif

// ============

#include <algorithm>
#include <cassert>
#include <utility>
#include <vector>

class HeavyLightDecomposition {
    std::vector<int> siz;
    std::vector<int> par;
    std::vector<int> hea;
    std::vector<int> in;
    std::vector<int> out;
    std::vector<int> dep;
    std::vector<int> rev;

    template <typename G>
    void dfs1(G &g, int v) {
        if (!g[v].empty() && (int) g[v][0] == par[v]) {
            std::swap(g[v][0], g[v].back());
        }
        for (auto &e : g[v]) {
            int u = (int)e;
            if (u != par[v]) {
                par[u] = v;
                dfs1(g, u);
                siz[v] += siz[u];
                if (siz[u] > siz[(int) g[v][0]]) {
                    std::swap(g[v][0], e);
                }
            }
        }
    }

    template <typename G>
    void dfs2(const G &g, int v, int &time) {
        in[v] = time;
        rev[time++] = v;
        for (auto &e : g[v]) {
            int u = (int)e;
            if (u == par[v]) {
                continue;
            }
            if (u == (int) g[v][0]) {
                hea[u] = hea[v];
            } else {
                hea[u] = u;
            }
            dep[u] = dep[v] + 1;
            dfs2(g, u, time);
        }
        out[v] = time;
    }

public:
    template <typename G>
    HeavyLightDecomposition(G &g, int root = 0) :
        siz(g.size(), 1),
        par(g.size(), root),
        hea(g.size(), root),
        in(g.size(), 0),
        out(g.size(), 0),
        dep(g.size(), 0),
        rev(g.size(), 0) {
        assert(root >= 0 && root < (int) g.size());
        dfs1(g, root);
        int time = 0;
        dfs2(g, root, time);
    }

    int subtree_size(int v) const {
        assert(v >= 0 && v < (int) siz.size());
        return siz[v];
    }

    int parent(int v) const {
        assert(v >= 0 && v < (int) par.size());
        return par[v];
    }

    int in_time(int v) const {
        assert(v >= 0 && v < (int) in.size());
        return in[v];
    }

    int out_time(int v) const {
        assert(v >= 0 && v < (int) out.size());
        return out[v];
    }

    int depth(int v) const {
        assert(v >= 0 && v < (int) dep.size());
        return dep[v];
    }

    int time_to_vertex(int t) const {
        assert(t >= 0 && t < (int) rev.size());
        return rev[t];
    }
    
    int la(int v, int k) const {
        assert(v >= 0 && v < (int) dep.size());
        assert(k >= 0);
        if (k > dep[v]) {
            return -1;
        }
        while (true) {
            int u = hea[v];
            if (in[u] + k <= in[v]) {
                return rev[in[v] - k];
            }
            k -= in[v] - in[u] + 1;
            v = par[u];
        }
        return 0;
    }
    
    int forward(int v, int dst) const {
        assert(v >= 0 && v < (int) dep.size());
        assert(dst >= 0 && dst < (int) dep.size());
        assert(v != dst);
        int l = lca(v, dst);
        if (l == v) {
            return la(dst, dep[dst] - dep[v] - 1);
        } else {
            return par[v];
        }
    }

    int lca(int u, int v) const {
        assert(u >= 0 && u < (int) dep.size());
        assert(v >= 0 && v < (int) dep.size());
        while (u != v) {
            if (in[u] > in[v]) {
                std::swap(u, v);
            }
            if (hea[u] == hea[v]) {
                v = u;
            } else {
                v = par[hea[v]];
            }
        }
        return u;
    }

    int dist(int u, int v) const {
        assert(u >= 0 && u < (int) dep.size());
        assert(v >= 0 && v < (int) dep.size());
        return dep[u] + dep[v] - 2 * dep[lca(u, v)];
    }

    std::vector<std::pair<int, int>> path(int u, int v, bool edge) const {
        assert(u >= 0 && u < (int) dep.size());
        assert(v >= 0 && v < (int) dep.size());
        std::vector<std::pair<int, int>> fromu, fromv;
        bool rev = false;
        while (true) {
            if (u == v && edge) {
                break;
            }
            if (in[u] > in[v]) {
                std::swap(u, v);
                std::swap(fromu, fromv);
                rev ^= true;
            }
            if (hea[u] == hea[v]) {
                fromv.emplace_back(in[v], in[u] + (int)edge);
                v = u;
                break;
            } else {
                fromv.emplace_back(in[v], in[hea[v]]);
                v = par[hea[v]];
            }
        }
        if (rev) {
            std::swap(fromu, fromv);
        }
        std::reverse(fromv.begin(), fromv.end());
        fromu.reserve(fromv.size());
        for (auto [x, y] : fromv) {
            fromu.emplace_back(y, x);
        }
        return fromu;
    }
    
    int jump(int u, int v, int k) const {
        assert(u >= 0 && u < (int) dep.size());
        assert(v >= 0 && v < (int) dep.size());
        assert(k >= 0);
        int l = lca(u, v);
        int dis = dep[u] + dep[v] - 2 * dep[l];
        if (k > dis) {
            return -1;
        }
        if (k <= dep[u] - dep[l]) {
            return la(u, k);
        } else {
            return la(v, dis - k);
        }
    }
    
    int meet(int u, int v, int w) const {
        return lca(u, v) ^ lca(v, w) ^ lca(w, u);
    }
};

// ============

int main() {
    i32 n, q;
    cin >> n >> q;
    Vec<Vec<i32>> g(n);
    REP(i, n - 1) {
        i32 u, v;
        cin >> u >> v;
        --u;
        --v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    HeavyLightDecomposition hld(g);
    while (q--) {
        i32 s, t;
        cin >> s >> t;
        --s;
        --t;
        i32 d = hld.dist(s, t);
        if (d % 2 == 0) {
            i32 lca = hld.lca(s, t);
            i32 s_l = hld.depth(s) - hld.depth(lca);
            if (s_l == d / 2) {
                i32 s_ = hld.forward(lca, s);
                i32 t_ = hld.forward(lca, t);
                cout << n - hld.subtree_size(s_) - hld.subtree_size(t_) << '\n';
            } else {
                if (s_l > d / 2) {
                    swap(s, t);
                    s_l = d - s_l;
                }
                i32 mid = hld.la(t, d / 2);
                i32 t_ = hld.forward(mid, t);
                i32 s_side = n - hld.subtree_size(mid);
                i32 t_size = hld.subtree_size(t_);
                cout << n - s_side - t_size << '\n';
            }
        } else {
            cout << 0 << '\n';
        }
    }
}
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