用来练习邻接表结构 poj3268 pku spfa

#include<stdio.h>
#include<string.h>
#define MAXN 101000
#define INF 2000000
struct NODE
{
    int v;
    int w;
    NODE *next;
}edge[MAXN],redge[MAXN],temp[MAXN*2];
int pos=0;
int ecost[MAXN];
int N,M,W,s,Q[MAXN];
bool vis[MAXN];
void spfa(int dir)//0为正向，1为反向
{
    int head,rear,u,i;
    NODE*ptr;
    head=0,rear=1;
    memset(vis,0,sizeof(vis));
    for(i=0;i<=N;i++)
        ecost[i]=INF;
    Q[0]=s;
    ecost[s]=0;
    while(head!=rear)
    {
          u=Q[head];
          head++;
          vis[u]=false;//出队列
          if(dir!=0)  ptr=edge[u].next;
          else ptr=redge[u].next;
          while(ptr)
          {
              if(ecost[ptr->v]>ecost[u]+ptr->w)
              {
                  ecost[ptr->v]=ecost[u]+ptr->w;
                  if(!vis[ptr->v])
                  {
                      Q[rear]=ptr->v;
                      rear++;
                      vis[ptr->v]=true;
                  }
              }
              ptr=ptr->next;
          }
    }
}
void addedge(int x,int y,int w)
{
    NODE *ptr=&temp[pos++];
    ptr->v=y;
    ptr->w=w;
    ptr->next=edge[x].next;
    edge[x].next=ptr;
    ptr=&temp[pos++];
    ptr->v=x;
    ptr->w=w;
    ptr->next=redge[y].next;
    redge[y].next=ptr;
}
int ans[MAXN],maxtime;
int main()
{
    int i,x,y,w;
    while(scanf("%d%d%d",&N,&M,&s)!=EOF)
    {
        pos=0;
        for(i=0;i<=N;i++)
        {
            edge[i].next=NULL;
            redge[i].next=NULL;
        }
        for(i=0;i<M;i++)
        {
            scanf("%d%d%d",&x,&y,&w);
            addedge(x,y,w);    
        }
        maxtime=0;
        memset(ans,0,sizeof(ans));
        spfa(0);
        for(i=1;i<=N;i++)
        {
            if(i!=s) ans[i]+=ecost[i];
        }
        spfa(1);
        for(i=1;i<=N;i++)
        {
            if(i!=s)
            {
                ans[i]+=ecost[i];
                if(ans[i]>maxtime)
                    maxtime=ans[i];
            }
        }
        printf("%d\n",maxtime);
    }
    return 0;
}