結果
問題 | No.2337 Equidistant |
ユーザー |
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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 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 1 |
other | AC * 28 |
ソースコード
#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;}