結果
問題 | No.1976 Cut then Connect |
ユーザー |
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提出日時 | 2023-05-08 19:28:04 |
言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
結果 |
AC
|
実行時間 | 171 ms / 2,000 ms |
コード長 | 4,229 bytes |
コンパイル時間 | 2,501 ms |
コンパイル使用メモリ | 212,500 KB |
最終ジャッジ日時 | 2025-02-12 21:02:28 |
ジャッジサーバーID (参考情報) |
judge5 / judge4 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 2 |
other | AC * 31 |
ソースコード
#line 1 "test/tree/RerootingDP.test.cpp"#define PROBLEM "https://yukicoder.me/problems/no/1976"#line 2 "template/template.hpp"#include <bits/stdc++.h>#define rep(i, s, n) for (int i = s; i < (int)(n); i++)#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)#define all(v) v.begin(), v.end()using ll = long long;using ld = long double;using ull = unsigned long long;template <typename T> bool chmin(T &a, const T &b) {if (a <= b) return false;a = b;return true;}template <typename T> bool chmax(T &a, const T &b) {if (a >= b) return false;a = b;return true;}namespace lib {using namespace std;} // namespace lib// using namespace lib;#line 2 "tree/RerootingDP.hpp"#line 4 "tree/RerootingDP.hpp"namespace lib {template <class E, class V, E (*merge)(E, E), E (*e)(), E (*put_edge)(V, int),V (*put_vertex)(E, int)>struct RerootingDP {struct edge {int to, idx, xdi;};RerootingDP(int _n = 0) : n(_n) { es.resize(n); }void add_edge(int u, int v, int idx1, int idx2) {es[u].push_back({v, idx1, idx2});es[v].push_back({u, idx2, idx1});}vector<V> build(int v = 0) {root = v;outs.resize(n);subdp.resize(n);in.resize(n), up.resize(n);int tnow = 0;dfs(root, -1, tnow);return subdp;}vector<V> reroot() {reverse_edge.resize(n);reverse_edge[root] = e();reverse_dp.resize(n);answers.resize(n);bfs(root);return answers;}V get(int r, int v) {if (r == v) return answers[r];if (!(in[v] < in[r] && up[r] <= up[v])) return subdp[v];int le = 0, ri = outs[v].size();while (ri - le > 1) {int md = (le + ri) / 2;if (in[es[v][md].to] <= in[r])le = md;elseri = md;}return reverse_dp[es[v][le].to];}const vector<edge> &operator[](int idx) const { return es[idx]; }private:int n, root;vector<vector<edge>> es;vector<vector<E>> outs;vector<E> reverse_edge;vector<V> subdp, reverse_dp, answers;vector<int> in, up;void dfs(int v, int p, int &t) {E val = e();in[v] = t++;for (auto &u : es[v]) {if (u.to == p && u.to != es[v].back().to) swap(u, es[v].back());if (u.to == p) continue;dfs(u.to, v, t);E nval = put_edge(subdp[u.to], u.idx);outs[v].emplace_back(nval);val = merge(val, nval);}subdp[v] = put_vertex(val, v);up[v] = t;}void bfs(int v) {int siz = outs[v].size();vector<E> lui(siz + 1), rui(siz + 1);lui[0] = e(), rui[siz] = e();for (int i = 0; i < siz; i++) lui[i + 1] = merge(lui[i], outs[v][i]);for (int i = siz - 1; i >= 0; i--)rui[i] = merge(outs[v][i], rui[i + 1]);for (int i = 0; i < siz; i++) {reverse_dp[es[v][i].to] = put_vertex(merge(merge(lui[i], rui[i + 1]), reverse_edge[v]), v);reverse_edge[es[v][i].to] =put_edge(reverse_dp[es[v][i].to], es[v][i].xdi);bfs(es[v][i].to);}answers[v] = put_vertex(merge(lui[siz], reverse_edge[v]), v);}};} // namespace lib#line 5 "test/tree/RerootingDP.test.cpp"using namespace lib;using P = pair<int,int>;P merge(P a, P b){return P(max(max(a.first,b.first),a.second+b.second),max(a.second,b.second));}P e(){return P(0,0);}P pute(P v, int id){return P(max(v.first,v.second+1),v.second+1);}P putv(P e, int id){return e;}int main(){int n; cin >> n;RerootingDP<P,P,merge,e,pute,putv> g(n);for (int i = 0; i < n-1; i++){int u, v; cin >> u >> v; u--, v--;g.add_edge(u,v,i,i);}g.build();g.reroot();int ans = n;for (int u = 0; u < n; u++){for (auto [v, idx, dxi] : g[u]){int x = g.get(u,v).first;int y = g.get(v,u).first;ans = min(ans,max({x,y,(x+1)/2+(y+1)/2+1}));}}cout << ans << endl;}