제출 #287353

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
287353		Namnamseo	경주 (Race) (IOI11_race)	C++17	100 / 100	2936 ms	50936 KiB

race

#include <bits/stdc++.h>
using namespace std;
#define sz(v) ((int)((v).size()))
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define coord_comp(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define v_index(v, x) (lower_bound(all(v),x)-(v).begin())
typedef pair<int,int> pp;
typedef long long ll;

int n,k;

vector<pp> edge[200001];

bool dead[200010];

int nt;
int pre_time[200010];
int pre_par [200010];
int pre_size[200010];
int pre_mcsz[200010];

void pre_dfs(int x){
	pre_size[x]=1;
	pre_mcsz[x]=0;
	pre_time[x]=nt;
	for(pp ep : edge[x]){
		int y = ep.first;
		if(dead[y] || (pre_time[y]==nt && pre_par[x]==y)) continue;
		pre_par[y]=x;
		pre_dfs(y);
		pre_mcsz[x] = max(pre_mcsz[x], pre_size[y]);
		pre_size[x] += pre_size[y];
	}
}

int find_cent(int root){
	++nt;
	pre_par[root] = -1;
	pre_dfs(root);
	int sz=pre_size[root];
	while(true){
		if(pre_mcsz[root] <= sz/2) break;
		for(pp ep:edge[root]){
			int y=ep.first;
			if(dead[y] || pre_par[root]==y) continue;
			if(pre_mcsz[root] == pre_size[y]){
				root=y; break;
			}
		}
	}
	return root;
}

int ans=2e9;

int par[200010];

void dfs_child(int x, int depth, int dc, set<pp>& s){
	s.insert({depth,dc});
	for(pp ep:edge[x]){
		int y=ep.first;
		if(dead[y] || par[x]==y) continue;
		par[y]=x;
		dfs_child(y, depth+ep.second, dc+1, s);
	}
}

inline void find_pairs(pp& t,multiset<pp>& s){
	if(t.first > k) return;
	auto it=s.lower_bound({k-t.first,0});
	if(it!=s.end() && it -> first == k-t.first){
		ans = min(ans, t.second + it->second);
	}
}

void treat_root(int x){
	vector<set<pp>> sets;
	for(pp ep:edge[x]){
		int y=ep.first;
		if(dead[y]) continue;
		par[y]=x;
		set<pp> ns;
		dfs_child(y, ep.second, 1, ns);
		sets.pb(ns);
	}
	multiset<pp> s;
	for(auto& ss:sets){
		for(pp t:ss) s.insert(t);
	}
	s.insert({0,0});
	for(auto& v:sets){
		for(auto t:v) s.erase(s.find(t));
		for(auto t:v) find_pairs(t, s);
		for(auto t:v) s.insert(t);
	}
}

int best_path(int N, int K, int H[][2], int L[]) {
	n = N; k = K;
	for(int i=0; i<n-1; ++i){
		int a=H[i][0],b=H[i][1],c=L[i];
		edge[a].pb({b,c});
		edge[b].pb({a,c});
	}

	queue<int> q;
	q.push(1);
	while(q.size()){
		int t = q.front(); q.pop();
		int cent = find_cent(t);
		treat_root(cent);
		dead[cent] = true;
		for(pp ep:edge[cent]){
			int y = ep.first;
			if(!dead[y]){
				q.push(y);
			}
		}
	}
	if(ans == int(2e9)) ans=-1;
	return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57