Submission #510067

#	Time	Username	Problem	Language	Result	Execution time	Memory
510067		CSQ31	Olympic Bus (JOI20_ho_t4)	C++17	5 / 100	1063 ms	3980 KiB

ho_t4

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int MAXN = 5e4+5;
const ll INF = 1e18;
#define sz(a) (int)(a.size())
ll c[MAXN],d[MAXN],dist[MAXN];
int n,m;
array<int,2>par[201];
vector<array<int,2>>g[201],gr[201];
bool block[MAXN],vis[201];
void djikstra(int v,vector<array<int,2>>*g){
	for(int i=1;i<=n;i++)dist[i] = INF,vis[i] = 0;
	dist[v] = 0;
	while(true){
		int u = 0;
		for(int i=1;i<=n;i++)if(dist[i] < dist[u] && !vis[i])u = i;
		if(!u)break;
		vis[u] = 1;
		for(auto x:g[u]){
			if(block[x[1]])continue;
			if(dist[u] + c[x[1]] < dist[x[0]]){
				dist[x[0]] = dist[u] + c[x[1]];
				par[x[0]] = {u,x[1]};
			}
		}
	}
}
ll odist[2][201]; //ori graph
ll rdist[2][201]; //reverse graph

vector<int>path[2];
vector<int>cut[2];
int main()
{
	cin>>n>>m;
	dist[0] = INF;
	vector<array<int,2>>edge;
	for(int i=0;i<m;i++){
		int v,u;
		cin>>v>>u>>c[i]>>d[i];
		g[v].push_back({u,i});
		gr[u].push_back({v,i});
		edge.push_back({v,u});
	}
	/*
	djikstra(1,g);
	for(int i=1;i<=n;i++)odist[0][i] = dist[i];
	if(dist[n] != INF){
		int cur = n;
		while(cur!=1){
			path[0].push_back(par[cur][1]);
			cur = par[cur][0];
		}
		reverse(path[0].begin(),path[0].end());
		cut[0].resize(sz(path[0]));
		for(int i=0;i<sz(path[0]);i++){
			int x = path[0][i];
			block[x] = 1;
			djikstra(1,g);
			cut[0][x] = dist[n];	
		}
	}*/
	ll ans = INF;
	for(int i=0;i<=m;i++){
		if(i!=m){
			block[i] = 1;
			c[m+1] = c[i];
			g[edge[i][1]].push_back({edge[i][0],m+1});
		}
		ll cost = d[i];
		djikstra(1,g);
	    cost+=dist[n];
		djikstra(n,g);
		cost+=dist[1];
		
		ans = min(ans,cost);
		
		if(i!=m){
			g[edge[i][1]].pop_back();
			block[i] = 0;
		}
	}
	if(ans == INF)ans = -1;
	cout<<ans;
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63