Submission #302447

#	Time	Username	Problem	Language	Result	Execution time	Memory
302447		Hemimor	Race (IOI11_race)	C++14	43 / 100	3042 ms	40312 KiB

race

#include "race.h"
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<P> vp;
typedef vector<vp> vvp;

const int inf=1<<30,MAX=1000001,NMAX=200000;
int res=inf,c[MAX],s[NMAX];
ll m;
bool vis[NMAX];
vp g[NMAX];

int Cdfs(int v,int p){
	s[v]=1;
	for(auto i:g[v]){
		int u=i.first;
		if(!vis[u]&&u!=p) s[v]+=Cdfs(u,v);
	}
	return s[v];
}

P Cdfs1(int v,int p,int S){
	P q={inf,0};
	int M=0,S_=S-1;
	for(auto i:g[v]){
		int u=i.first;
		if(!vis[u]&&u!=p){
			q=min(q,Cdfs1(u,v,S));
			M=max(M,s[u]);
			S_-=s[u];
		}
	}
	return min(q,{max(M,S_),v});
}

int Cent(int v){
	Cdfs(v,-1);
	return Cdfs1(v,-1,s[v]).second;
}

int t,len,tp;

void DFS(int v,int par=-1){
	if(len>=res||t>m) return;
	if(t==m) res=min(res,len);
	if(tp==0&&t<m) res=min(res,c[m-t]+len);
	if(tp==1) c[t]=min(c[t],len);
	if(tp==2) c[t]=inf;
	for(auto p:g[v]){
		int u=p.first;
		if(!vis[u]&&u!=par){
			len++;
			t+=p.second;
			DFS(u,v);
			len--;
			t-=p.second;
		}
	}
}

void Rec(int v){
	v=Cent(v);
	vis[v]=1;
	vvp b;
	for(auto p:g[v]){
		t=p.second,len=1,tp=0;
		DFS(p.first);
		t=p.second,len=1,tp=1;
		DFS(p.first);
	}
	for(auto p:g[v]){
		t=p.second,len=1,tp=2;
		DFS(p.first);
	}
	for(auto p:g[v]){
		int u=p.first;
		if(!vis[u]) Rec(u);
	}
}

int best_path(int N, int K, int H[][2], int L[]){
	m=K;
	fill(c,c+MAX,inf);
	for(int i=0;i<N-1;i++){
		int u=H[i][0],v=H[i][1];
		g[u].push_back({v,L[i]});
		g[v].push_back({u,L[i]});
	}
	Rec(0);
	if(res==inf) res=-1;
	return res;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 0 / 57