結果

問題 No.2337 Equidistant
ユーザー ei1333333
提出日時 2022-08-22 19:23:02
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 1,273 ms / 4,000 ms
コード長 3,905 bytes
コンパイル時間 2,649 ms
コンパイル使用メモリ 208,964 KB
最終ジャッジ日時 2025-01-31 02:52:37
ジャッジサーバーID
(参考情報)
judge3 / 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 #
プレゼンテーションモードにする

#include<bits/stdc++.h>
using namespace std;
#line 2 "graph/tree/doubling-lowest-common-ancestor.hpp"
#line 2 "graph/graph-template.hpp"
/**
* @brief Graph Template()
*/
template< typename T = int >
struct Edge {
int from, to;
T cost;
int idx;
Edge() = default;
Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {}
operator int() const { return to; }
};
template< typename T = int >
struct Graph {
vector< vector< Edge< T > > > g;
int es;
Graph() = default;
explicit Graph(int n) : g(n), es(0) {}
size_t size() const {
return g.size();
}
void add_directed_edge(int from, int to, T cost = 1) {
g[from].emplace_back(from, to, cost, es++);
}
void add_edge(int from, int to, T cost = 1) {
g[from].emplace_back(from, to, cost, es);
g[to].emplace_back(to, from, cost, es++);
}
void read(int M, int padding = -1, bool weighted = false, bool directed = false) {
for(int i = 0; i < M; i++) {
int a, b;
cin >> a >> b;
a += padding;
b += padding;
T c = T(1);
if(weighted) cin >> c;
if(directed) add_directed_edge(a, b, c);
else add_edge(a, b, c);
}
}
inline vector< Edge< T > > &operator[](const int &k) {
return g[k];
}
inline const vector< Edge< T > > &operator[](const int &k) const {
return g[k];
}
};
template< typename T = int >
using Edges = vector< Edge< T > >;
#line 4 "graph/tree/doubling-lowest-common-ancestor.hpp"
/**
* @brief Doubling-Lowest-Common-Ancestor()
* @docs docs/doubling-lowest-common-ancestor.md
*/
template< typename T >
struct DoublingLowestCommonAncestor : Graph< T > {
public:
using Graph< T >::g;
vector< int > dep;
vector< int > sum;
vector< vector< int > > table;
const int LOG;
explicit DoublingLowestCommonAncestor(int n)
: Graph< T >(n), LOG(32 - __builtin_clz(g.size())) {}
explicit DoublingLowestCommonAncestor(const Graph< T > &g)
: LOG(32 - __builtin_clz(g.size())), Graph< T >(g) {}
void build(int root = 0) {
dep.assign(g.size(), 0);
sum.assign(g.size(), 0);
table.assign(LOG, vector< int >(g.size(), -1));
dfs(root, -1, 0);
for(int k = 0; k + 1 < LOG; k++) {
for(int i = 0; i < (int)table[k].size(); i++) {
if(table[k][i] == -1) table[k + 1][i] = -1;
else table[k + 1][i] = table[k][table[k][i]];
}
}
}
int lca(int u, int v) {
if(dep[u] > dep[v]) swap(u, v);
v = climb(v, dep[v] - dep[u]);
if(u == v) return u;
for(int i = LOG - 1; i >= 0; i--) {
if(table[i][u] != table[i][v]) {
u = table[i][u];
v = table[i][v];
}
}
return table[0][u];
}
int climb(int u, int k) {
if(dep[u] < k) return -1;
for(int i = LOG - 1; i >= 0; i--) {
if((k >> i) & 1) u = table[i][u];
}
return u;
}
int dist(int u, int v) {
return dep[u] + dep[v] - 2 * dep[lca(u, v)];
}
int size(int u) {
return sum[u];
}
private:
void dfs(int idx, int par, int d) {
table[0][idx] = par;
dep[idx] = d;
sum[idx] = 1;
for(auto &to : g[idx]) {
if(to != par) {
sum[to] = sum[idx] + to.cost;
dfs(to, idx, d + 1);
sum[idx] += sum[to];
}
}
}
};
int main() {
int N, Q;
cin >> N >> Q;
DoublingLowestCommonAncestor< int > g(N);
g.read(N - 1);
g.build();
while(Q--) {
int a, b;
cin >> a >> b;
--a, --b;
int d = g.dist(a, b);
if(d % 2 == 1) {
cout << 0 << endl;
continue;
}
d /= 2;
int lca = g.lca(a, b);
if(g.dist(a, lca) == d) {
cout << N - g.size(g.climb(a, d - 1)) - g.size(g.climb(b, d - 1)) << endl;
} else {
if(g.dist(a, lca) > g.dist(b, lca)) {
swap(a, b);
}
cout << g.size(g.climb(b, d)) - g.size(g.climb(b, d - 1)) << endl;
}
}
}
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