信息学奥赛一本通1253：抓住那头牛

//#include<iostream>
//#include<queue>
//using namespace std;
//
//const int maxn=1e5+5;
//struct point{
//    int x;
//    int time;
//};
//
//struct point qs[maxn];
//int n,k;
//bool map[maxn];
//
//void find(int s,int t)
//{
//
//}
//
//int main()
//{
//    int n,k;
//    cin>>n>>k;
//    memset(map,true,sizeof(map));
//    memset(qs,0,sizeof(qs));
//
//    //    int cnt=0;
////    if(n==0&&k>n)
////    {
////        n=n+1;
////        cnt++;
////    }
////    int i=n;
////    while(abs(k-i)>=2*i||abs(k-(2*i))<abs(k-i))
////    {
////        i=i*2;
////        cnt++;
////    }
////    cnt+=abs(k-i);
////    cout<<cnt<<endl;
////    return 0;
//
//
//
//}
//

#include<iostream>
#include<queue>

using namespace std;

struct st
{
    int loc;
    int t;
};
const int maxn=1e5+5;
queue<st> q;
bool vis[maxn];

int main()
{
    int n,k;
    cin>>n>>k;
    st start{n,0};
    q.push(start);
    //int steps=0;
    vis[n]=true;
    while(!q.empty())
    {
        st tmp=q.front();
        if(tmp.loc==k)
        {
            cout<<tmp.t<<endl;
            break;
        }
//        else if(tmp.loc>k)
//        {
//            cout<<tmp.t+(tmp.loc-k)<<endl;
//            break;
//        }
        else
        {
            if(!vis[tmp.loc+1]&&tmp.loc+1<=maxn)
            {
                st right{tmp.loc+1,tmp.t+1};
                q.push(right);
                vis[right.loc]=true;
            }
           if(!vis[tmp.loc-1]&&tmp.loc-1>=0)
           {
               st left{tmp.loc-1,tmp.t+1};
               q.push(left);
               vis[left.loc]=true;
           }
            if(!vis[tmp.loc*2]&&tmp.loc*2<=maxn)
            {
                st prod2{tmp.loc*2,tmp.t+1};
                q.push(prod2);
                vis[prod2.loc]=true;
            }
            q.pop();
        }
        
    }
    return 0;
}



//------------------------上面是RE代码----------------------
//由&&引发的RE，无限RE，调了很长时间...tnnd


//注意左右边界
//注意&&
//注意bool数组的意义

#include<iostream>
#include<cstdio>
#include<queue>

using namespace std;

struct st
{
    int loc;
    int t;
};

const int maxn=1e5+5;
queue<st> q;
bool vis[maxn];

int main()
{
    int n,k;
    cin>>n>>k;
    st start;
    start.loc=n;
    start.t=0;
    q.push(start);
    vis[start.loc]=true;
    while(!q.empty())
    {
        st tmp;
        tmp=q.front();
        if(tmp.loc==k)
        {
            cout<<tmp.t<<endl;
            break;
        }
        st node;
        if(tmp.loc+1<=maxn&&!vis[tmp.loc+1])
        {

            node.loc=tmp.loc+1;
            node.t=tmp.t+1;
            q.push(node);
            vis[node.loc]=true;
        }
       if(tmp.loc-1>=0&&!vis[tmp.loc-1])
       {
           
           node.loc=tmp.loc-1;
           node.t=tmp.t+1;
           q.push(node);
           vis[node.loc]=true;
       }
        if(tmp.loc*2<=maxn&&!vis[tmp.loc*2])
        {
            node.loc=tmp.loc*2;
            node.t=tmp.t+1;
            q.push(node);
            vis[node.loc]=true;
        }
        q.pop();
    }
    return 0;
}