广搜

#include#include#includeusingnamespacestd;constintMAXN=100010;intstep[MAXN],vis[MAXN];

queueQ;intBFS(intn,intk)

{intnext,head;

step[n]=0;

vis[n]=1;

Q.push(n);while(!Q.empty())

{

head=Q.front();

Q.pop();for(inti=0;i<3;i++)

{if(i==0) next=head-1;elseif(i==1) next=head+1;elsenext=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)returnstep[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}

}

}intmain()

{intn,k;while(scanf("%d%d",&n,&k)!=EOF)

{

memset(vis,0,sizeof(vis));if(n>=k) printf("%d\n",n-k);elseprintf("%d\n",BFS(n,k));

}return0;

}