Submission #492950

#	Time	Username	Problem	Language	Result	Execution time	Memory
492950		1ne	Race (IOI11_race)	C++14	0 / 100	92 ms	119516 KiB

race

#include "race.h"

#include<bits/stdc++.h>
using namespace std;
vector<set<pair<int,int>>>adj(1e6);
int k=0;
vector<int>sub(1e6,0);
vector<int>ans(1e6,0);
vector<int>aux(1e6,0);
int answer = INT_MAX;
int kk = -1;
int bookmark = 0;
void dfs (int cur,int par,int cost,int len,int fill){
	if (fill){
		if (aux[cost]<bookmark){
			aux[cost] = bookmark;
			ans[cost] = len;
		}
		else if (len<ans[cost]){
			ans[cost] = len;
			aux[cost] = bookmark;
		}
	}
	else{
		if (aux[kk - cost]==bookmark){
			if (len + ans[kk - cost]<answer){
				answer = min(answer,len + ans[kk-cost]);
			}
			if (cost ==kk){
				answer = min(answer,len);
			}
		}
	}
	for (auto x:adj[cur]){
		if (x.first!=par){
			dfs(x.first,cur,cost + x.second,len + 1,fill);
		}
	}
}
void getsub(int u,int par){
	sub[u]=1;
	k++;
	for (auto x:adj[u]){
		if (x.first!=par){
			getsub(x.first,u);
			sub[u]+=sub[x.first];
		}
	}
}
int getcentroid(int u,int par){
	for (auto x:adj[u]){
		if (x.first!=par){
			if (sub[x.first]>k/2){
				return getcentroid(x.first,u);
			}
		}
	}
	return u;
}
void decomposition(int u,int par){
	k = 0;
	getsub(u,u);
	int c = getcentroid(u,u);
	if (par==-1){
		par=c;
	}
	bookmark++;
	for (auto x:adj[c]){
		dfs(x.first,c,x.second,1,0);
		dfs(x.first,c,x.second,1,1);
	}
	for (auto x:adj[c]){
		adj[x.first].erase({c,x.second});
		//adj[c].erase(x);
		decomposition(x.first,c);
	}
}
void build(){
	decomposition(0,-1);
}
int best_path(int N, int K, int H[][2], int L[])
{
	kk = K;
 	for (int i = 0;i<N-1;++i){
 		adj[H[i][0]].insert({H[i][1],L[i]});
 		adj[H[i][1]].insert({H[i][0],L[i]});
 	}
 	build();
 	if (answer==INT_MAX){
 		return -1;
 	}
 	return answer;
}

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