hdu 4318 SPFA 最短路

#include<iostream>
#include<stdio.h>
#include<queue>
#include<iomanip>
#include<string>
#include<cstring>
using namespace std;
#define N 50005
struct Edgenode
{
int v,next;
double cost;
}Edge[N*55];
int edgenumber,head
;
int visited
;
double Sum
;
void SAFA(int s,int t,int total);
void addedge(int i,int v1,double value)
{
Edge[edgenumber].v=v1;
Edge[edgenumber].cost=value;
Edge[edgenumber].next=head[i];
head[i]=edgenumber++;
}

int main()
{
int n,i,j,k,value,s,t,total;
while(scanf("%d",&n)!=EOF)
{
memset(head,-1,sizeof(head));
edgenumber=0;
for(i=1;i<=n;i++)
{
cin>>j;
while(j--)
{
cin>>k>>value;
addedge(i,k,value/100.00);
}
}
cin>>s>>t>>total;
for(int q=0;q<=n;++q) { visited[q]=0; Sum[q]=total;}
SAFA(s,t,total);
if(Sum[t]>=total)
cout<<"IMPOSSIBLE!"<<endl;
else
printf("%.2lf\n",Sum[t]);
}
return 0;
}

void SAFA(int s,int t,int total)
{
queue<int> q;
q.push(s);
double temp;
int i,j,k;
Sum[s]=0;
visited[s]=true;
while(!q.empty())
{
i=q.front();
q.pop();
for(j=head[i];j!=-1;j=Edge[j].next)
{
k=Edge[j].v;
temp=Sum[i]+(total-Sum[i])*Edge[j].cost;
if(Sum[k]<=temp) continue;
Sum[k]=temp;
if(visited[k]) continue;
q.push(k);
visited[k]=1;
}
visited[i]=0;
}
}