--hdu2717->搜索的范围控制

#include<stdio.h>
#include<string.h>
#include<queue>
#include<algorithm>
using namespace std;
int vis[300010];

int bfs(int x,int ans){

    queue<int>q;
    queue<int>num;
    q.push(x);
    num.push(0);
    while(!q.empty()){

        int xx = q.front();
        int nn = num.front();
        num.pop();
        q.pop();

        if(xx == ans)return nn;
        if(xx>=0&&vis[xx-1] == 0){
            q.push(xx-1);
            num.push(nn+1);
            vis[xx-1] = 1;
        }
        if(xx+1<=ans&&vis[xx+1] == 0){
            q.push(xx+1);
            num.push(nn+1);
            vis[xx+1] = 1;
        }

        if(2*xx <=ans*2&&vis[2*xx] == 0){
            q.push(2*xx);
            num.push(nn+1);
            vis[2*xx] = 1;
        }

    }

}

int main(){


    int n,m;

    while(~scanf("%d%d",&n,&m)){
         memset(vis,0,sizeof(vis));
         vis[n]=1;
         printf("%d\n",bfs(n,m));

    }
}