結果
| 問題 |
No.2337 Equidistant
|
| コンテスト | |
| ユーザー |
 iiljj
|
| 提出日時 | 2023-06-02 22:31:49 |
| 言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
| 結果 |
AC
|
| 実行時間 | 832 ms / 4,000 ms |
| コード長 | 18,038 bytes |
| コンパイル時間 | 1,951 ms |
| コンパイル使用メモリ | 153,104 KB |
| 最終ジャッジ日時 | 2025-02-13 19:22:38 |
|
ジャッジサーバーID （参考情報） |
judge1 / judge5 |
（要ログイン）
| ファイルパターン | 結果 |
|---|---|
| sample | AC * 1 |
| other | AC * 28 |
ソースコード
/* #region Head */
// #include <bits/stdc++.h>
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert> // assert.h
#include <cmath> // math.h
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U> using um = unordered_map<T, U>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqa = priority_queue<T, vc<T>, greater<T>>;
template <class T> using us = unordered_set<T>;
#define TREP(T, i, m, n) for (T i = (m), i##_len = (T)(n); i < i##_len; ++(i))
#define TREPM(T, i, m, n) for (T i = (m), i##_max = (T)(n); i <= i##_max; ++(i))
#define TREPR(T, i, m, n) for (T i = (m), i##_min = (T)(n); i >= i##_min; --(i))
#define TREPD(T, i, m, n, d) for (T i = (m), i##_len = (T)(n); i < i##_len; i += (d))
#define TREPMD(T, i, m, n, d) for (T i = (m), i##_max = (T)(n); i <= i##_max; i += (d))
#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define REPIR(itr, ds) for (auto itr = ds.rbegin(); itr != ds.rend(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define ISIZE(x) ((int)(x).size())
#define PERM(c) \
sort(ALL(c)); \
for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());
#define CEIL(a, b) (((a) + (b)-1) / (b))
#define endl '\n'
constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr int IINF = 1'000'000'007LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;
template <typename T> istream &operator>>(istream &is, vc<T> &vec) { // vector 入力
for (T &x : vec) is >> x;
return is;
}
template <typename T> ostream &operator<<(ostream &os, const vc<T> &vec) { // vector 出力 (for dump)
os << "{";
REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "" : ", ");
os << "}";
return os;
}
template <typename T> ostream &operator>>(ostream &os, const vc<T> &vec) { // vector 出力 (inline)
REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "\n" : " ");
return os;
}
template <typename T, size_t _Nm> istream &operator>>(istream &is, array<T, _Nm> &arr) { // array 入力
REP(i, 0, SIZE(arr)) is >> arr[i];
return is;
}
template <typename T, size_t _Nm> ostream &operator<<(ostream &os, const array<T, _Nm> &arr) { // array 出力 (for dump)
os << "{";
REP(i, 0, SIZE(arr)) os << arr[i] << (i == i_len - 1 ? "" : ", ");
os << "}";
return os;
}
template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var) { // pair 入力
is >> pair_var.first >> pair_var.second;
return is;
}
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &pair_var) { // pair 出力
os << "(" << pair_var.first << ", " << pair_var.second << ")";
return os;
}
// map, um, set, us 出力
template <class T> ostream &out_iter(ostream &os, const T &map_var) {
os << "{";
REPI(itr, map_var) {
os << *itr;
auto itrcp = itr;
if (++itrcp != map_var.end()) os << ", ";
}
return os << "}";
}
template <typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &map_var) {
return out_iter(os, map_var);
}
template <typename T, typename U> ostream &operator<<(ostream &os, const um<T, U> &map_var) {
os << "{";
REPI(itr, map_var) {
auto [key, value] = *itr;
os << "(" << key << ", " << value << ")";
auto itrcp = itr;
if (++itrcp != map_var.end()) os << ", ";
}
os << "}";
return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, const us<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, const pq<T> &pq_var) {
pq<T> pq_cp(pq_var);
os << "{";
if (!pq_cp.empty()) {
os << pq_cp.top(), pq_cp.pop();
while (!pq_cp.empty()) os << ", " << pq_cp.top(), pq_cp.pop();
}
return os << "}";
}
// tuple 出力
template <size_t N = 0, bool end_line = false, typename... Args> ostream &operator<<(ostream &os, tuple<Args...> &a) {
if constexpr (N < std::tuple_size_v<tuple<Args...>>) {
os << get<N>(a);
if constexpr (N + 1 < std::tuple_size_v<tuple<Args...>>) {
os << ' ';
} else if constexpr (end_line) {
os << '\n';
}
return operator<< <N + 1, end_line>(os, a);
}
return os;
}
template <typename... Args> void print_tuple(tuple<Args...> &a) { operator<< <0, true>(cout, a); }
void pprint() { cout << endl; }
template <class Head, class... Tail> void pprint(Head &&head, Tail &&...tail) {
cout << head;
if (sizeof...(Tail) > 0) cout << ' ';
pprint(move(tail)...);
}
// dump
#define DUMPOUT cerr
void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head &&head, Tail &&...tail) {
DUMPOUT << head;
if (sizeof...(Tail) > 0) DUMPOUT << ", ";
dump_func(move(tail)...);
}
// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmax(T &xmax, const U &x, Comp comp = {}) {
if (comp(xmax, x)) {
xmax = x;
return true;
}
return false;
}
// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmin(T &xmin, const U &x, Comp comp = {}) {
if (comp(x, xmin)) {
xmin = x;
return true;
}
return false;
}
// ローカル用
#ifndef ONLINE_JUDGE
#define DEBUG_
#endif
#ifndef MYLOCAL
#undef DEBUG_
#endif
#ifdef DEBUG_
#define DEB
#define dump(...) \
DUMPOUT << " " << string(#__VA_ARGS__) << ": " \
<< "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl \
<< " ", \
dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
#define VAR(type, ...) \
type __VA_ARGS__; \
assert((cin >> __VA_ARGS__));
template <typename T> istream &operator,(istream &is, T &rhs) { return is >> rhs; }
template <typename T> ostream &operator,(ostream &os, const T &rhs) { return os << ' ' << rhs; }
struct AtCoderInitialize {
static constexpr int IOS_PREC = 15;
static constexpr bool AUTOFLUSH = false;
AtCoderInitialize() {
ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
cout << fixed << setprecision(IOS_PREC);
if (AUTOFLUSH) cout << unitbuf;
}
} ATCODER_INITIALIZE;
void Yn(bool p) { cout << (p ? "Yes" : "No") << endl; }
void YN(bool p) { cout << (p ? "YES" : "NO") << endl; }
template <typename T> constexpr void operator--(vc<T> &v, int) noexcept {
for (int i = 0; i < ISIZE(v); ++i) v[i]--;
}
template <typename T> constexpr void operator++(vc<T> &v, int) noexcept {
for (int i = 0; i < ISIZE(v); ++i) v[i]++;
}
/* #endregion */
// #include <atcoder/all>
// using namespace atcoder;
/* #region Graph */
// エッジ（本来エッジは双方向だが，ここでは単方向で管理）
template <class weight_t = int, class flow_t = int> struct Edge {
int src; // エッジ始点となる頂点
int dst; // エッジ終点となる頂点
weight_t weight; // 重み
flow_t cap;
Edge() : src(0), dst(0), weight(0) {}
Edge(int src, int dst, weight_t weight) : src(src), dst(dst), weight(weight) {}
Edge(int src, int dst, weight_t weight, flow_t cap) : src(src), dst(dst), weight(weight), cap(cap) {}
// Edge 標準出力
friend ostream &operator<<(ostream &os, Edge &edge) {
os << "(" << edge.src << " -> " << edge.dst << ", " << edge.weight << ")";
return os;
}
};
// 同じ頂点を始点とするエッジ集合
template <class weight_t = int, class flow_t = int> class Node : public vc<Edge<weight_t, flow_t>> {
public:
int idx;
Node() : vc<Edge<weight_t, flow_t>>() {}
// void add(int a, int b, weight_t w, flow_t cap) { this->emplace_back(a, b, w, cap); };
};
// graph[i] := 頂点 i を始点とするエッジ集合
template <class weight_t = int, class flow_t = int> class Graph : public vc<Node<weight_t, flow_t>> {
public:
Graph() : vc<Node<weight_t, flow_t>>() {}
Graph(int n) : vc<Node<weight_t, flow_t>>(n) { REP(i, 0, n)(*this)[i].idx = i; }
/** 単方向 */
void add_arc(int a, int b, weight_t w = 1, flow_t cap = 1) { (*this)[a].emplace_back(a, b, w, cap); }
/** 双方向 */
void add_edge(int a, int b, weight_t w = 1, flow_t cap = 1) { add_arc(a, b, w, cap), add_arc(b, a, w, cap); }
/** ノード追加 */
int add_node() {
int idx = (int)this->size();
this->emplace_back();
Node<weight_t, flow_t> &node = this->back();
node.idx = idx;
return idx;
}
};
// using Array = vc<Weight>;
// using Matrix = vc<Array>;
/* #endregion */
/* #region LCA */
template <class weight_t = int, class flow_t = int> class LCA {
public:
const int n = 0;
const int log2_n = 0;
vc<vc<int>> parent;
vc<int> depth;
vc<weight_t> weight_distances;
using G = Graph<weight_t, flow_t>;
LCA() {}
// コンストラクタ，前処理 O(N log N)
LCA(const G &g, int root)
: n(g.size()), log2_n(log2(n) + 1), parent(log2_n, vc<int>(n)), depth(n), weight_distances(n) {
dfs(g, root, -1, 0, (weight_t)0);
REP(k, 0, log2_n - 1) REP(v, 0, SIZE(g)) parent[k + 1][v] = (parent[k][v] < 0) ? -1 : parent[k][parent[k][v]];
}
// 根からの距離と1つ先の頂点を求める
void dfs(const G &g, int v, int p, int d, weight_t w) {
parent[0][v] = p, depth[v] = d;
weight_distances[v] = w;
for (const Edge<weight_t, flow_t> &e : g[v])
if (e.dst != p) dfs(g, e.dst, v, d + 1, w + e.weight);
}
// 頂点 u, v の LCA を求めて返す，O(log N)
int get(int u, int v) const {
if (depth[u] > depth[v]) std::swap(u, v);
// 深い方を浅い方と同じ浅さまで移動することで，LCA までの深さを同じにする
REP(k, 0, log2_n) if ((depth[v] - depth[u]) >> k & 1) v = parent[k][v];
if (u == v) return u;
// 二分探索で LCA を求める
REPR(k, log2_n - 1, 0) if (parent[k][u] != parent[k][v]) u = parent[k][u], v = parent[k][v];
return parent[0][u];
}
// 頂点 v から dist だけ根のほうに遡った頂点を返す．
// dist が根までの距離よりも大きいときは -1 を返す．
int get_par(int v, int dist) const {
// dist 遡れない
int v_init_depth = get_depth(v);
if (v_init_depth < dist) return -1;
int u_depth = v_init_depth - dist;
// 深い方を浅い方と同じ浅さまで移動することで，LCA までの深さを同じにする
REP(k, 0, log2_n) if ((depth[v] - u_depth) >> k & 1) v = parent[k][v];
return v;
}
// 根を深さ 0 として，頂点 v の深さを返す．O(1).
int get_depth(int v) const {
assert(0 <= v && v < n);
return depth[v];
}
// 頂点 u, v の間を最短距離で結ぶときの辺数を返す．O(log N).
int get_distance(int u, int v) const {
const int r = get(u, v);
return depth[u] + depth[v] - 2 * depth[r];
}
// 頂点 u, v の間を最短距離で結ぶときの距離を返す．O(log N).
weight_t get_weight_distance(int u, int v) const {
const int r = get(u, v);
return weight_distances[u] + weight_distances[v] - weight_distances[r] * 2;
}
// {(src->lca), (lca->dst)} を返す
array<vc<int>, 2> get_path2(const int src, const int dst) const {
const int common = get(src, dst);
vc<int> path_from_src = {src};
{
int v = src;
while (v != common) {
v = parent[0][v];
path_from_src.push_back(v);
}
}
vc<int> path_from_dst = {dst};
{
int v = dst;
while (v != common) {
v = parent[0][v];
path_from_dst.push_back(v);
}
}
reverse(ALL(path_from_dst));
vc<int> &path_to_dst = path_from_dst;
return {path_from_src, path_to_dst};
}
// src -> dst のパスを返す
vc<int> get_path(const int src, const int dst) const {
auto [path_from_src, path_to_dst] = get_path2(src, dst);
path_from_src.reserve(ISIZE(path_from_src) + ISIZE(path_to_dst));
TREP(int, i, 1, ISIZE(path_to_dst)) { path_from_src.push_back(path_to_dst[i]); }
return path_from_src;
}
};
/* #endregion */
/* #region EulerTour */
template <class weight_t = int> struct EulerTour {
Graph<weight_t> &graph;
vc<int> in, out; // 頂点→ツアー上のインデックス，の写像
vc<int> tour; // ツアー上のインデックス→頂点，の写像
vc<int> sz; // sz[i] := i を根とする部分木のサイズ
vc<weight_t> weight;
vc<int> sign; // 1（行きがけ） or -1（帰りがけ）
int cnt;
EulerTour(int n, Graph<weight_t> &graph) : graph(graph), in(n), out(n), sz(n) {
tour.reserve(2 * n);
weight.reserve(2 * n);
sign.reserve(2 * n);
}
void dfs(int cur, int par) {
for (Edge<weight_t> &e : graph[cur]) {
if (e.dst == par) continue;
weight.push_back(e.weight), sign.push_back(1), tour.push_back(e.dst);
in[e.dst] = cnt++;
dfs(e.dst, cur);
weight.push_back(-e.weight), sign.push_back(-1), tour.push_back(e.dst);
out[e.dst] = cnt++;
sz[e.dst] = (out[e.dst] - in[e.dst] + 1) / 2;
}
}
int execute(int root) {
cnt = 0;
weight.push_back(0), sign.push_back(1), tour.push_back(root);
in[root] = cnt++;
dfs(root, -1);
weight.push_back(0), sign.push_back(-1), tour.push_back(root);
out[root] = cnt++;
sz[root] = (out[root] - in[root] + 1) / 2;
return cnt;
}
};
/* #endregion */
// Problem
void solve() {
VAR(ll, n, q);
vll a(n - 1), b(n - 1);
REP(i, 0, n - 1) cin >> a[i], b[i];
a--, b--;
vll s(q), t(q);
REP(i, 0, q) cin >> s[i], t[i];
s--, t--;
Graph<> graph(n);
REP(i, 0, n - 1) graph.add_edge(a[i], b[i]);
LCA<> lca(graph, 0);
EulerTour tour(n, graph);
tour.execute(0); // 0 が根
REP(i, 0, q) {
ll d = lca.get_distance(s[i], t[i]);
if (d % 2 == 1) {
pprint(0);
continue;
}
ll l = lca.get(s[i], t[i]);
ll d2 = d / 2;
ll dist_sl = lca.get_distance(s[i], l);
ll dist_tl = d - dist_sl;
// ll par_s = lca.get_par(s[i], d2);
// ll par_t = lca.get_par(t[i], d2);
if (dist_sl >= d2) {
// s から m へは一直線，t からは？
if (dist_tl >= d2) {
// s からも t からも同じ距離に LCA がある
// -> m から伸びる枝のうち，s, t をそれぞれ含む部分木を除く全ての頂点が答え
ll ex_s = lca.get_par(s[i], d2 - 1);
ll ex_t = lca.get_par(t[i], d2 - 1);
ll ans = n - tour.sz[ex_s] - tour.sz[ex_t];
pprint(ans);
} else {
// m の部分木のうち，s を含む枝を除いた個数が答え．
ll m = lca.get_par(s[i], d2);
ll ex_s = lca.get_par(s[i], d2 - 1);
ll ans = tour.sz[m] - tour.sz[ex_s];
pprint(ans);
}
} else {
// s から m へは一直線ではない．t からは一直線．
// -> m の部分木のうち，t を含む枝を除いた個数が答え．
ll m = lca.get_par(t[i], d2);
ll ex_t = lca.get_par(t[i], d2 - 1);
ll ans = tour.sz[m] - tour.sz[ex_t];
// dump(ex_t, m, tour.sz[m], tour.sz[ex_t]);
pprint(ans);
}
}
}
// entry point
int main() {
solve();
return 0;
}