hdu-1874 SPFA

noip day1 少得100分，看错题了。。。

/*
 * hdu-1874 SPFA
 * mike-w
 * 2011-11-12
 */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAXN 500
#define MAXM 5000
#define QSIZE 5000
#define INF 999999

typedef struct _lnode
{
	int node,weight,next;
}lnode;

int hhead[MAXN],ID;
int que[MAXN],inq[MAXN],head,tail,len;
lnode list[MAXM];
int M,N,S,T;
int d[MAXN];

int push(int e)
{
	que[tail++]=e;
	len++;
	if(tail==QSIZE)
		tail=0;
	return 0;
}

int pop(int *e)
{
	*e=que[head++];
	len--;
	if(head==QSIZE)
		head=0;
	return 0;
}

int insert(int start,int end,int weight)
{
	int pos,nxt;
	if(hhead[start]==-1)
	{
		pos=hhead[start]=ID++;
		list[pos].node=end;
		list[pos].weight=weight;
		list[pos].next=-1;
	}
	else
	{
		pos=hhead[start];
		nxt=list[pos].next;
		pos=list[pos].next=ID++;
		list[pos].node=end;
		list[pos].weight=weight;
		list[pos].next=nxt;
	}
	return 0;
}

int SPFA(void)
{
	int i,x,pos;
	head=tail=len=0;
	for(i=0;i<N;i++)
	{
		inq[i]=head=tail=len=0;
		d[i]=INF;
	}

	push(S);
	inq[S]=1;
	d[S]=0;
	while(len>0)
	{
		pop(&x);
		inq[x]=0;
		for(pos=hhead[x];pos!=-1;pos=list[pos].next)
		{
			if(d[x]+list[pos].weight<d[list[pos].node])
			{
				d[list[pos].node]=d[x]+list[pos].weight;
				if(!inq[list[pos].node])
					push(list[pos].node),inq[list[pos].node]=1;
			}
		}
	}
	if(d[T]==INF)
		return -1;
	else
		return d[T];
}

int main(void)
{
	int i,t1,t2,t3;
#ifndef ONLINE_JUDGE
	freopen("in","r",stdin);
#endif
	while(scanf("%d%d",&N,&M)!=EOF)
	{
		for(i=0;i<=N;i++)
			hhead[i]=-1;
		ID=0;
		for(i=1;i<=M;i++)
		{
			scanf("%d%d%d",&t1,&t2,&t3);
			insert(t1,t2,t3);
			insert(t2,t1,t3);
		}
		scanf("%d%d",&S,&T);
		printf("%d\n",SPFA());
	}
	return 0;
}