結果

問題 No.2337 Equidistant
ユーザー 👑 emthrm
提出日時 2023-06-02 21:40:57
言語 C++23
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 932 ms / 4,000 ms
コード長 3,880 bytes
コンパイル時間 7,002 ms
コンパイル使用メモリ 263,060 KB
実行使用メモリ 49,304 KB
最終ジャッジ日時 2024-12-28 16:57:08
合計ジャッジ時間 19,456 ms
ジャッジサーバーID
(参考情報)
judge4 / 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 #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
IOSetup() {
std::cin.tie(nullptr);
std::ios_base::sync_with_stdio(false);
std::cout << fixed << setprecision(20);
}
} iosetup;
struct LowestCommonAncestorByDoubling {
std::vector<int> depth;
vector<int> sub;
explicit LowestCommonAncestorByDoubling(
const std::vector<std::vector<int>>& graph)
: is_built(false), n(graph.size()),
table_h(std::countr_zero(std::bit_floor(graph.size())) + 1),
graph(graph) {
depth.resize(n);
sub.resize(n, 1);
parent.resize(table_h, std::vector<int>(n));
}
void build(int root = 0) {
is_built = true;
dfs(-1, root, 0);
for (int i = 0; i + 1 < table_h; ++i) {
for (int ver = 0; ver < n; ++ver) {
parent[i + 1][ver] =
(parent[i][ver] == -1 ? -1 : parent[i][parent[i][ver]]);
}
}
}
int query(int u, int v) const {
assert(is_built);
if (depth[u] > depth[v]) std::swap(u, v);
for (int i = 0; i < table_h; ++i) {
if ((depth[v] - depth[u]) >> i & 1) v = parent[i][v];
}
if (u == v) return u;
for (int i = table_h - 1; i >= 0; --i) {
if (parent[i][u] != parent[i][v]) {
u = parent[i][u];
v = parent[i][v];
}
}
return parent.front()[u];
}
int distance(const int u, const int v) const {
assert(is_built);
return depth[u] + depth[v] - depth[query(u, v)] * 2;
}
int level_ancestor(int v, const int d) const {
assert(is_built);
if (depth[v] < d) return -1;
for (int i = depth[v] - d, bit = 0; i > 0; i >>= 1, ++bit) {
if (i & 1) v = parent[bit][v];
}
return v;
}
int jump(const int u, const int v, const int d) const {
assert(is_built);
if (d == 0) [[unlikely]] return u;
const int l = query(u, v), d_lu = depth[u] - depth[l];
if (d_lu == d) return l;
if (d_lu > d) return level_ancestor(u, depth[u] - d);
return level_ancestor(v, depth[l] + (d - d_lu));
}
private:
bool is_built;
const int n, table_h;
const std::vector<std::vector<int>> graph;
std::vector<std::vector<int>> parent;
void dfs(const int par, const int ver, const int cur_depth) {
depth[ver] = cur_depth;
parent.front()[ver] = par;
for (const int e : graph[ver]) {
if (e != par) {
dfs(ver, e, cur_depth + 1);
sub[ver] += sub[e];
}
}
}
};
int main() {
int n, q; cin >> n >> q;
vector<vector<int>> graph(n);
REP(_, n - 1) {
int a, b; cin >> a >> b; --a; --b;
graph[a].emplace_back(b);
graph[b].emplace_back(a);
}
LowestCommonAncestorByDoubling lca(graph);
lca.build();
while (q--) {
int s, t; cin >> s >> t; --s; --t;
const int d = lca.distance(s, t);
if (d % 2 == 1) {
cout << 0 << '\n';
} else {
const int root = lca.jump(s, t, d / 2);
const int ad_s = lca.jump(root, s, 1), ad_t = lca.jump(root, t, 1);
if (lca.depth[ad_s] == lca.depth[ad_t]) {
cout << n - lca.sub[ad_s] - lca.sub[ad_t] << '\n';
} else {
const int ch = (lca.depth[ad_s] > lca.depth[ad_t] ? ad_s : ad_t);
cout << lca.sub[root] - lca.sub[ch] << '\n';
}
}
}
return 0;
}
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