poj3278

Posted 2020-09-14

#include<iostream>
#define MAX 100001
int john,cow;
int queue[MAX];
int vis[MAX];
int ans;

void bfs()
{
    int tail,head;
    tail=head=0;
    int start=john;
    queue[tail++]=start;
    vis[start]=1;
    while(head!=tail)
    {
        int cur,next;
        cur=queue[head++];
        if(cur==cow)
        {
            ans=vis[cur]-1;
            return;
        }
        next=cur;
        next=cur+1;
        if(next>=0&&next<MAX&&vis[next]==0)
        {
            vis[next]=vis[cur]+1;
            queue[tail++]=next;
        }

        next=cur-1;
        if(next>=0&&next<MAX&&vis[next]==0)
        {
            vis[next]=vis[cur]+1;
            queue[tail++]=next;
        }
        next=2*cur;
        if(next>=0&&next<MAX&&vis[next]==0)
        {
            vis[next]=vis[cur]+1;
            queue[tail++]=next;
        }
    }
}

int main()
{
    //freopen("input.txt","r",stdin);
    std::cin>>john>>cow;
    for(int i=0;i<MAX;i++)
        vis[i]=0;
    bfs();
    std::cout<<ans;
    return 0;
}