Catch That Cow

#include<stdio.h>
#include<queue>
#include<string.h>
using namespace std;
const int MAXN=100010;

int step[MAXN],vis[MAXN];
queue<int>Q;

int BFS(int n,int k)
{
    int next,head;
    step[n]=0; 
    vis[n]=1;
    Q.push(n);
    while(!Q.empty())
    {
        head=Q.front();
        Q.pop();
        for(int i=0;i<3;i++)
        {
            if(i==0) next=head-1;
            else if(i==1) next=head+1;
            else next=head*2;
            if(next>MAXN || next<0) continue;
            if(!vis[next]) 
            {
                vis[next]=1;
                Q.push(next);
                step[next]=step[head]+1;
            }
            if(k==next) return step[next];
        //广搜搜索的深度第一次相等的就是深度最小的那个支结点，所以没必要再比较哪个最少了
        }
    
    }
}

int main()
{
    int n,k;
    while(scanf("%d%d",&n,&k)!=EOF)
    {
        memset(vis,0,sizeof(vis));
        if(n>=k) printf("%d\n",n-k);
        else printf("%d\n",BFS(n,k));
    }
    return 0;
}