pat a1003 Bellman-Ford求最短路径

题目：

https://pintia.cn/problem-sets/994805342720868352/problems/994805523835109376 

#include<cstdio>
#include<cstring>
#include<vector>
#include<set>
#include<algorithm> 
using namespace std;

const int maxv=510;
const int inf=0x3fffffff;

struct Node
{
	int v;
	int dis;
	Node(int _v,int _dis)
	{
		v=_v;
		dis=_dis;
	}
};

vector<Node> adj[maxv];
int n,m,st,ed,weight[maxv];
int d[maxv],w[maxv],num[maxv];
set<int> pre[maxv];

void Bellman(int s)
{
	fill(d,d+maxv,inf);
	memset(num,0,sizeof(num));
	memset(w,0,sizeof(w));
	d[s]=0;
	w[s]=weight[s];
	num[s]=1;
	for(int i=0;i<n-1;i++)
	{
		for(int u=0;u<n;u++)
		{
			for(int j=0;j<adj[u].size();j++)
			{
				int v=adj[u][j].v;
				int dis=adj[u][j].dis;
				if(d[u]+dis<d[v])
				{
					d[v]=d[u]+dis;
					w[v]=w[u]+weight[v];
					num[v]=num[u];
					pre[v].clear();
					pre[v].insert(u);
				}
				else if(d[u]+dis==d[v])
				{
					if(w[u]+weight[v]>w[v])
					{
						w[v]=w[u]+weight[v];
					}
					pre[v].insert(u);
					num[v]=0;
					set<int>::iterator it;
					for(it=pre[v].begin();it!=pre[v].end();it++)
					{
						num[v]+=num[*it];
					}
				}
			}
		}		
	}	
}


int main()
{
	scanf("%d%d%d%d",&n,&m,&st,&ed);
	for(int i=0;i<n;i++)
	{
		scanf("%d",&weight[i]);
	}
	int u,v,wt;
	for(int i=0;i<m;i++)
	{
		scanf("%d%d%d",&u,&v,&wt);
		adj[u].push_back(Node(v,wt));
		adj[v].push_back(Node(u,wt));
	}
	Bellman(st);
	printf("%d %d\n",num[ed],w[ed]);
	return 0;
}