Submission #1267477

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267477		WH8	Dreaming (IOI13_dreaming)	C++20	100 / 100	51 ms	19648 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
using ll=long long;
vector<vector<pair<int, ll>>> al(100005);
vector<tuple<ll, int, ll>> dist(100005, {1e12, -1, 0}); 
// dist, previous node, previous edge weight 
vector<int> curtree;
vector<ll> guys;
vector<bool> vis(100005);

void dfs(int cur, pair<int,ll> pre){
	curtree.push_back(cur);
	for(auto [to, cost]:al[cur]){
		//~ printf("at %d, to %d, cost %d\n", cur, to, cost);
		if(to==pre.first)continue;
		get<0>(dist[to])=get<0>(dist[cur])+cost;
		get<1>(dist[to])=cur;
		get<2>(dist[to])=cost;
		dfs(to, {cur, cost});
	}
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    for(int i=0;i<M;i++){
		al[A[i]].push_back({B[i], T[i]});
		al[B[i]].push_back({A[i],T[i]});
	}
	int x, y;
	ll ans=0;
	for(int i=0;i<N;i++){
		if(vis[i])continue;
		dist[i]={0, -1, 0};
		dfs(i, {-1, 0});
		x=i;
		for(auto node : curtree){
			if(get<0>(dist[node])>get<0>(dist[x])){
				x=node;
			}
		}
		for(auto node : curtree){
			dist[node]={1e12, -1, 0};
		}
		curtree.clear();
		dist[x]={0, -1, 0};
		dfs(x, {-1, 0});
		y=x;
		for(auto node : curtree){
			if(get<0>(dist[node])>get<0>(dist[y])){
				y=node;
			}
			vis[node]=true;
		}
		curtree.clear();
		ll dl=get<0>(dist[y]);
		ans=max(ans, dl);
		
		vector<pair<int,int>> dia;
		int cur=y;
		ll cv=dl, sm=0;
		while(get<1>(dist[cur]) != -1){
			sm+=get<2>(dist[cur]);
			cv=min(cv, max(dl-sm, sm));
			cur=get<1>(dist[cur]);
		}		
		//~ printf("i=%d, x %d, y %d, dl is %d, cv is %d\n",i,x,y,dl, cv);
		guys.push_back(cv);
	}
	sort(guys.begin(),guys.end(), greater<ll>());
	return max({ans, ((int)guys.size() >= 2 ? guys[0]+L+guys[1]: 0), ((int)guys.size() >= 3? guys[1]+2*L+guys[2]:0)});
}

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 18 / 18
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23