poj3278 优先队列

给你两个点N,K，从N到K，你有三种移动方案：①N-1②N+1③N*2让你用这三种方案达到K点，问最少需要多少步？

#include<iostream>
#include<algorithm>
#include<queue>
#include<string.h>
#include<cstdio>
#define max 100001
using namespace std;
struct node
{
    int n;
    int step;
    bool friend operator <  ( node  a , node  b )
    {
        return a.step>b.step;
    }
};
int N,K;
int vis[100010];
void bfs(int N)
{
    int ans;
    priority_queue<node>q;
    node p,tem;
    p.step=0;
    p.n=N;
    q.push(p);
    while(!q.empty())
    {
        tem=q.top();
        q.pop();
        if(tem.n==K)
        {
            printf("%d\n",tem.step);
           // printf("ans=%d\n",tem.n);
            return ;
        }
        if(tem.n-1>=0&&tem.n-1<max&&!vis[tem.n-1])
        {
            vis[tem.n-1]=1;
            p.n=tem.n-1;
            p.step=tem.step+1;
            q.push(p);
        }
        if(tem.n+1>=0&&tem.n+1<max&&!vis[tem.n+1])
        {
            vis[tem.n+1]=1;
            p.n=tem.n+1;
            p.step=tem.step+1;
            q.push(p);
        }
        if(tem.n*2>=0&&tem.n*2<max&&!vis[tem.n*2])
        {
            vis[tem.n*2]=1;
            p.n=tem.n*2;
            p.step=tem.step+1;
            q.push(p);
        }
    }
}
int main()
{
    while(scanf("%d%d",&N,&K)!=EOF)
    {
        memset(vis,0,sizeof(vis));
        bfs(N);
       // printf("%d\n",bfs(N));
    }
    return 0;
}