Submission #1140919

#	Time	Username	Problem	Language	Result	Execution time	Memory
1140919		why1	Race (IOI11_race)	C++20	0 / 100	8 ms	14400 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;

#define ll long long 
#define pii pair<ll,ll>
#define fi first
#define se second
#define sz size()
#define pb push_back

const int N = 2e5;

int n,k;
int h[N+1][2],l[N+1];

vector<pii> g[N+1];
ll dw[N+1],d[N+1];
set<pii> st[N+1];
ll ans=1e9;

void calc(int v,int pr){
	for(auto [to,i]: g[v]){
		if(to!=pr){
			dw[to]=dw[v]+l[i];
			d[to]=d[v]+1;
			calc(to,v);
		}
	}
}

void dfs(int v,int pr){	
	st[v].insert({dw[v],v});
	for(auto [to,i]: g[v]){
		if(to!=pr){
			dfs(to,v);	
			if(st[v].sz<st[to].sz)
				st[v].swap(st[to]);
			for(auto [D,j]: st[to]){
				ll x=k+2*dw[v]-D;	
				auto it=st[v].lower_bound({x,0});
				if(it!=st[v].end() && it->fi==x){
					ans=min(ans,d[j]+d[it->se]-2*d[v]);
				}
			}
			for(auto j: st[to]){
				st[v].insert(j);
			}
		}
	}
}

int best_path(int n, int k, int h[][2], int l[]){
//void solve(){

	//cin>>n>>k;
	for(int i = 1; i <= n-1; i++){
		//cin>>h[i][0]>>h[i][1]>>l[i];
		h[i][0]++,h[i][1]++;
		g[h[i][0]].pb({h[i][1],i});
		g[h[i][1]].pb({h[i][0],i});
	}

	calc(1,-1);
	dfs(1,-1);
/*
	for(int i = 1; i <= n; i++){
		cout<<i<<": ";
		for(auto j: st[i]){
			cout<<"{"<<j.fi<<" "<<j.se<<"} ";
		}
		cout<<"\n";
	}
*/
	if(ans==1e9)
		ans=-1;
	//cout<<ans<<"\n";
	return ans;
}
/*
int main(){
	solve();
	return 0;
}
*/

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