SPFA首题！hdu-2544

刚才看了一下SPFA，很简单。时间有限，见BAIDU。说是BELLMAN的优化，不过我觉得更像DIJKSTRA

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define SIZE 200
#define QSIZE 200
#define INF 9999999
int f[SIZE][SIZE];
int d[SIZE];
int inq[SIZE];
int que[QSIZE],head,tail,len;
int N,M;

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

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

int main(void)
{
#ifndef ONLINE_JUDGE
	freopen("in","r",stdin);
#endif
	int i,x,t1,t2,t3;
	while(scanf("%d%d",&N,&M),M||N)
	{
		memset(f,0,sizeof(f));
		for(i=0;i<M;i++)
		{
			scanf("%d%d%d",&t1,&t2,&t3);
			f[t1][t2]=f[t2][t1]=t3;
		}
		for(i=1;i<=N;i++)
			inq[i]=0, d[i]=INF;
		head=tail=len=0;
		push(1);
		inq[1]=1;
		d[1]=0;
		while(len>0)
		{
			pop(&x);
			inq[x]=0;
			for(i=1;i<=N;i++)
				if(f[x][i] && d[x]+f[x][i]<d[i])
				{
					d[i]=d[x]+f[x][i];
					if(!inq[i])
						push(i),inq[i]=1;
				}
		}
		printf("%d\n",d[N]);
	}
	return 0;
}