USACO3.2.6多源最短路径和SPFA实现

#include<iostream>
#include<queue>
using namespace std;
const int maxn=99999999;
const int edge_maxn = 3000;
const int point_maxn = 805;
int m,cown,mina;
struct node
{
int v;
int w;
int next;
}edge[edge_maxn];
int pre[point_maxn];
int n;

queue<int>Q;
int dirs[point_maxn],cow[edge_maxn];
bool vis[point_maxn];
void Init()
{
memset(pre,-1,sizeof(pre));
memset(cow,0,sizeof(cow));
int x,y,z,temp;
int index=1;
int i;
for(i=1;i<=cown;i++)
{
scanf("%d",&temp);
cow[temp]++;
}
for(i=1;i<=m;i++)
{
scanf("%d%d%d",&x,&y,&z);
edge[index].v=y;
edge[index].w=z;
edge[index].next=pre[x];
pre[x]=index++;
swap(x,y);
edge[index].v=y;
edge[index].w=z;
edge[index].next=pre[x];
pre[x]=index++;
}
}
void SPFA(int mu)
{
int start,i;
start=mu;
while(!Q.empty())
{
Q.pop();
}
memset(vis,0,sizeof(vis));
//fill(dirs,dirs+point_maxn,maxn);
for(i=1;i<=n;i++)
dirs[i]=99999999;
dirs[start]=0;
vis[start]=1;
Q.push(start);
while(!Q.empty())
{
int top=Q.front();
Q.pop();
vis[top]=0;
for(int j=pre[top];j!=-1;j=edge[j].next)
{
int e=edge[j].v;
if(dirs[e]>edge[j].w+dirs[top])
{
dirs[e]=edge[j].w+dirs[top];
if(!vis[e])
{
Q.push(e);
vis[e]=1;
}
}
}
}
int add=0;
for(i=1;i<=n;i++)
{
if(start!=i)
add+=cow[i]*dirs[i];
}
if(mina>add)
mina=add;
}
int main()
{
int i;
while(scanf("%d%d%d",&cown,&n,&m)!=EOF && (n!=0 || m!=0))
{
mina=9999999;
Init();
for(i=1;i<=n;i++)
{
SPFA(i);
}
printf("%d\n",mina);
}
return 0;
}