POJ 3278 Catch That Cow

#include<stdio.h>
#include<iostream>
#include<cstdio>
#include<queue>
#include<memory.h>
#define maxn 100005
using namespace std;
queue<int> q;
int step[maxn];
int visit[maxn];
int n,k;
int head,next;
int bfs()
{
    q.push(n);
    step[n]=0;
    visit[n]=1;
    while(!q.empty())
    {
        head=q.front();
        q.pop();
        for(int i=0;i<3;i++)
        {
            if(i==0)next=head+1;
            if(i==1)next=head-1;
            if(i==2)next=head*2;
            if(next>maxn||next<0)
                continue;
            if(!visit[next])
            {
                q.push(next);
                step[next]=step[head]+1;
                visit[next]=1;
            }
            if(next==k)
                return step[next];
        }
    }
    return -1;
}
int main()
{
    memset(step,0,sizeof(step));
    memset(visit,0,sizeof(visit));
    cin>>n>>k;
    cout<<bfs()<<endl;
    return 0;
}