HDU-2717

这题和1548没啥区别，但是中间还是出现了几波迷之错误

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AC代码：

#include<iostream>  
#include<cstring>  
#include<cstdio>  
#include<queue>  
#define MM(x,y) memset(x,y,sizeof(x))
typedef long long ll;
using namespace std;  
const int N=1000000;  
int a[N];  
struct node{  
    int x;  
    ll step;  
};  
queue<node>Q;  
int vis[N];  
int n,k;
bool check(int x)
{
	if(x>=0&&x<=N&&!vis[x])
	 return 1;
    else
      return 0;
}
int bfs()  
{  
    node now,next;  
    int i;  
    now.step=0;  
    now.x=n;  
    Q.push(now);  
    vis[n]=1;  
    while(!Q.empty())  
    {  
        now=Q.front();  
        Q.pop();  
        if(now.x==k)  
            return now.step;  
        next.x=now.x*2;  
        if(check(next.x))  
        {  
            next.step=now.step+1;  
            Q.push(next);  
            vis[next.x]=1;  
        }  
        next.x=now.x+1;  
        if(check(next.x))  
        {  
            next.step=now.step+1;  
            Q.push(next);  
            vis[next.x]=1;  
        } 
        next.x=now.x-1;  
        if(check(next.x))  
        {  
            next.step=now.step+1;  
            Q.push(next);  
            vis[next.x]=1;  
        } 
    }
    return -1;
}  
int main()  
{  
    int i,j,sum;  
    while(cin>>n>>k)
    {  
        while(!Q.empty())  
        {  
            Q.pop();  
        }  
        MM(vis,0);  
        cout<<bfs()<<endl;
    }  
    return 0;  
}