POJ 3278 Catch That Cow

POJ_3278

    这个是个比较简单的BFS的题目。

#include<stdio.h>
#include<string.h>
int dis[200010],q[200010];
int main()
{
    int i,j,N,K,front,rear,n,newn;
    while(scanf("%d%d",&N,&K)==2)
    {
        memset(dis,-1,sizeof(dis));
        dis[N]=0;
        front=rear=0;
        q[rear++]=N;
        while(front<rear)
        {
            n=q[front++];
            if(n==K)
                break;
            if(n<K)
            {
                newn=n-1;
                if(dis[newn]<0)
                {
                    dis[newn]=dis[n]+1;
                    q[rear++]=newn;
                }
                newn=n+1;
                if(dis[newn]<0)
                {
                    dis[newn]=dis[n]+1;
                    q[rear++]=newn;
                }
                newn=2*n;
                if(dis[newn]<0)
                {
                    dis[newn]=dis[n]+1;
                    q[rear++]=newn;
                }
            }
            else
            {
                newn=n-1;
                if(dis[newn]<0)
                {
                    dis[newn]=dis[n]+1;
                    q[rear++]=newn;
                }
            }
        }
        printf("%d\n",dis[K]);
    }
    return 0;    
}