結果

問題 No.1976 Cut then Connect
ユーザー noya2noya2
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
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ソースコード

diff #
プレゼンテーションモードにする

#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;
else
ri = 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;
}
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