SDUT OJ 2138 最短路

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int n,h[1010];

struct M
{
    int data;
    struct M *next;
}*head[1010];

struct Q
{
    int step;
    int site;
};

void init()
{
    int i;
    for(i = 1;i <= n; i++)
    {
        head[i] = (struct M *)malloc(sizeof(struct M));
        head[i]->data = -1;
        head[i]->next = NULL;
    }
}

void link(int u,int v)
{
    struct M *p1,*p2,*q;
    q = (struct M * )malloc(sizeof(struct M));
    q->next = NULL;
    q->data = v;
    for(p1 = head[u],p2 = p1->next;p2 != NULL; p1 = p1->next,p2 = p2->next)
    {
        if(p1->data < v && p2->data > v)
        {
            q->next = p1->next;
            p1->next = q;
            return;
        }
        else if(p2->data == v) {free(q);return;}
    }
    p1->next = q;
}

int seek(int mb)
{
    int s,e,temp,step;
    struct M *p;
    struct Q q[1010];
    s = e = 0;
    q[e].site = mb;
    q[e++].step = 0;
    while(s < e)
    {
        mb = q[s].site;
        temp = q[s++].step;
        for(p = head[mb];p != NULL;p = p->next)
        {
            if(!h[p->data])
            {
                if(p->data == 1) return temp;
                q[e].site = p->data;
                q[e++].step = temp + 1;
                h[p->data] = 1;
            }
        }
    }
    return -1;
}

int main()
{
    int m,i,u,v,step;
    while(scanf("%d %d",&n,&m) == 2)
    {
        if(n == 1) {printf("0\n");continue;}
        init();
        for(i = 0;i < m; i++)
        {
            scanf("%d %d",&u,&v);
            link(u,v);
        }
        memset(h,0,sizeof(h));
        h[n] = 1;
        step = seek(n);
        if(step >= 0) printf("%d\n",step+1);
        else printf("NO\n");
    }
    return 0;
}