Submission #684052

#	Time	Username	Problem	Language	Result	Execution time	Memory
684052		fuad27	Race (IOI11_race)	C++17	100 / 100	1240 ms	51660 KiB

race

#include "race.h"
#include<bits/stdc++.h>
using namespace std;
const int N =200'010; 
long long K=0;
vector<pair<int, long long>> g[N];
vector<bool> R(N);
int dp[N];
int dfs(int at, int p) {
	dp[at]=1;
	for(auto to:g[at]) {
		if(to.first!=p and !R[to.first]) {
			dp[at]+=dfs(to.first,at);
		}
	}
	return dp[at];
}
int get_centroid(int at, int sz, int p) {
	for(auto to:g[at]) {
		if(to.first==p or R[to.first])continue;
		if(dp[to.first]*2>sz)return get_centroid(to.first,sz,at);
	}
	return at;
}
long long res=1e18;
map<long long, int> mp;
map<long long, int> mp2;
void dfs1(int at, int p, long long w, int d=1) {
	if(mp2.find(w)==mp2.end() or mp2[w]>d) {
		mp2[w]=d;
		if(mp.find(K-w)!=mp.end())
		res=min(res,(long long)mp2[w]+mp[K-w]);
	}
	for(auto to:g[at]) {
		if(R[to.first])continue;
		if(to.first==p)continue;
		dfs1(to.first,at,w+to.second,d+1);
	}
}
void get(int at) {

	mp.clear();
	mp2.clear();
	mp[0]=0;
	for(auto to:g[at]) {
		if(R[to.first])continue;
		dfs1(to.first,at,to.second);
		for(auto i:mp2) {
			if(mp.find(i.first)==mp.end())mp[i.first]=i.second;
			else mp[i.first]=min(mp[i.first],i.second);
		}
		mp2.clear();
	}
}
void centroid(int n=0) {
	int C=get_centroid(n,dfs(n,-1),-1);
	get(C);
	R[C]=1;
	for(auto to:g[C]) {
		if(!R[to.first])centroid(to.first);
	}
}
int best_path(int n, int k, int h[][2], int l[])
{
	K=k;
	for(int i = 0;i<n-1;i++) {
		g[h[i][0]].push_back({h[i][1],l[i]});
		g[h[i][1]].push_back({h[i][0],l[i]});
	}
	centroid();
	if(res==1e18)return -1;
	return res;
}

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