結果

問題 No.2337 Equidistant
コンテスト
ユーザー AngrySadEight
提出日時 2025-12-18 23:05:16
言語 C++17
(gcc 13.3.0 + boost 1.89.0)
結果
AC  
実行時間 1,256 ms / 4,000 ms
コード長 7,491 bytes
記録
記録タグの例:
初AC ショートコード 純ショートコード 純主流ショートコード 最速実行時間
コンパイル時間 3,877 ms
コンパイル使用メモリ 191,456 KB
実行使用メモリ 79,756 KB
最終ジャッジ日時 2025-12-18 23:05:43
合計ジャッジ時間 23,015 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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 #
raw source code 

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

void dfs(vector<vector<ll>> &graph, vector<bool> &isvisited, ll v, vector<ll> &treedp){
    isvisited[v] = true;
    ll ret = 1;
    for (ll x: graph[v]){
        if (isvisited[x]){
            continue;
        }
        dfs(graph, isvisited, x, treedp);
        ret += treedp[x];
    }
    treedp[v] = ret;
}

int main() {
    ll N, Q;
    cin >> N >> Q;
    vector<ll> A(N - 1);
    vector<ll> B(N - 1);
    for (ll i = 0; i < N - 1; i++){
        cin >> A[i] >> B[i];
        A[i]--;
        B[i]--;
    }
    vector<ll> S(Q);
    vector<ll> T(Q);
    for (ll i = 0; i < Q; i++){
        cin >> S[i] >> T[i];
        S[i]--;
        T[i]--;
    }
    vector<vector<ll>> graph(N, vector<ll>(0));
    for (ll i = 0; i < N - 1; i++){
        graph[A[i]].push_back(B[i]);
        graph[B[i]].push_back(A[i]);
    }
    queue<ll> que;
    vector<ll> dist(N, N + 1);
    vector<ll> prev(N, -1);
    que.push(0);
    dist[0] = 0;
    while (que.size()){
        ll p = que.front();
        que.pop();
        for (ll x: graph[p]){
            if (dist[x] < N){
                continue;
            }
            dist[x] = dist[p] + 1;
            prev[x] = p;
            que.push(x);
        }
    }
    // debug(prev);
    vector<vector<ll>> doubling(N, vector<ll>(18));
    for (ll i = 0; i < N; i++){
        doubling[i][0] = prev[i];
    }
    for (ll i = 0; i < 17; i++){
        for (ll j = 0; j < N; j++){
            if (doubling[j][i] == -1){
                doubling[j][i + 1] = -1;
                continue;
            }
            doubling[j][i + 1] = doubling[doubling[j][i]][i];
        }
    }
    
    vector<bool> isvisited(N, false);
    vector<ll> treedp(N, 0);
    dfs(graph, isvisited, 0, treedp);

    for (ll i = 0; i < Q; i++){
        ll ds = dist[S[i]];
        ll dt = dist[T[i]];
        ll tar_s = S[i];
        ll tar_t = T[i];
        if (ds > dt){
            ll diffs = ds - dt;
            for (ll j = 0; j < 18; j++){
                if ((diffs >> j) & 1){
                    tar_s = doubling[tar_s][j];
                }
            }
        }
        else if (ds < dt){
            ll diffs = dt - ds;
            for (ll j = 0; j < 18; j++){
                if ((diffs >> j) & 1){
                    tar_t = doubling[tar_t][j];
                }
            }
        }
        if (tar_s == tar_t){
            ll lca = tar_s;
            ll d_two = (dist[S[i]] + dist[T[i]] - 2 * dist[lca]);
            if (d_two % 2 == 1){
                cout << 0 << endl;
                continue;
            }
            if (dist[S[i]] < dist[T[i]]){
                ll cent_n = T[i];
                ll d_h = d_two / 2 - 1;
                for (ll j = 0; j < 18; j++){
                    if ((d_h >> j) & 1){
                        cent_n = doubling[cent_n][j];
                    }
                }
                ll cent = prev[cent_n];
                cout << treedp[cent] - treedp[cent_n] << endl;
            }
            else{
                ll cent_n = S[i];
                ll d_h = d_two / 2 - 1;
                for (ll j = 0; j < 18; j++){
                    if ((d_h >> j) & 1){
                        cent_n = doubling[cent_n][j];
                    }
                }
                ll cent = prev[cent_n];
                cout << treedp[cent] - treedp[cent_n] << endl;   
            }
            continue;
        }
        
        for (ll j = 17; j >= 0; j--){
            if (doubling[tar_s][j] != doubling[tar_t][j]){
                tar_s = doubling[tar_s][j];
                tar_t = doubling[tar_t][j];
            }
        }
        
        ll lca = prev[tar_s];
        ll d_two = (dist[S[i]] + dist[T[i]] - 2 * dist[lca]);
        if (d_two % 2 == 1){
            cout << 0 << endl;
            continue;
        }
        if (dist[S[i]] == dist[T[i]]){
            cout << N - treedp[tar_s] - treedp[tar_t] << endl;
        }
        else if (dist[S[i]] < dist[T[i]]){
            ll cent_n = T[i];
            ll d_h = d_two / 2 - 1;
            for (ll j = 0; j < 18; j++){
                if ((d_h >> j) & 1){
                    cent_n = doubling[cent_n][j];
                }
            }
            ll cent = prev[cent_n];
            cout << treedp[cent] - treedp[cent_n] << endl;
        }
        else{
            ll cent_n = S[i];
            ll d_h = d_two / 2 - 1;
            for (ll j = 0; j < 18; j++){
                if ((d_h >> j) & 1){
                    cent_n = doubling[cent_n][j];
                }
            }
            ll cent = prev[cent_n];
            cout << treedp[cent] - treedp[cent_n] << endl;
        }
    }
}
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