poj 3278——Catch That Cow

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;

int abs(int x){
        return x<0?-x:x;
}

int dis[300005];
int n,k;
void bfs()
{
        queue<int> q;
        q.push(n);
        dis
=0;
        while(!q.empty()){
                int tmp=q.front();
                q.pop();
                if((abs(n-k)>abs(tmp+1-k)||tmp+1<=k)&&(dis[tmp+1]==-1||dis[tmp+1]>dis[tmp]+1)){
                        dis[tmp+1]=dis[tmp]+1;
                        q.push(tmp+1);
                }
                if((abs(n-k)>abs(tmp-1-k)||tmp-1<=k&&tmp-1>=0)&&(dis[tmp-1]==-1||dis[tmp-1]>dis[tmp]+1)){
                        dis[tmp-1]=dis[tmp]+1;
                        q.push(tmp-1);
                }
                if(abs(n-k)>abs(tmp*2-k)&&tmp!=0&&(dis[tmp*2]==-1||dis[tmp*2]>dis[tmp]+1)){
                        dis[tmp*2]=dis[tmp]+1;
                        q.push(tmp*2);
                }
        }
}

int main()
{

        scanf("%d%d",&n,&k);
        memset(dis,-1,sizeof(dis));
        if(k<=n){
                printf("%d\n",n-k);
                return 0;
        }
        bfs();
        printf("%d\n",dis[k]);
        return 0;
}