poj 3278 Catch That Cow (BFS)

题意：

    牛逃跑了，主人用最短的时间追到牛（在直线上）

    很裸的bfs ,郁闷啊忘了判断重复了，RE ,WA !

   

#include<stdio.h>
#define N 100005
int n,k;
int stack[N],vis[N];
int main()
{

    scanf("%d%d",&n,&k);
    int di=0,top=1,first=0,last=1;
    int sum=0;stack[0]=n,vis[n]=1;
    while(di!=top)
    {
        last--;
        int num=stack[di++];
        if(num!=k)
        {

             if(num+1<=100000&&!vis[num+1])
             {
              vis[num+1]=1;
              first++;
              stack[top++]=num+1;
              top%=N;
             }
             if(2*num<=100000&&!vis[num*2])
             {
             vis[num*2]=1;
             stack[top++]=num*2;
             top%=N;
             first++;
             }
             if(num>0&&!vis[num-1])
             {
             vis[num-1]=1;
             stack[top++]=num-1;
             top%=N;
             first++;
             }

        }
        else
        {
            break;
        }
        if(last==0)
        {
           sum++;

           last=first;first=0;
        }
        di%=N;
    }
    printf("%d\n",sum);
    return 0;
}