当时我们校内比赛 我一看就是一道搜索题 结果没认真看 用的DFS怎么查 也查不出来  课下用的BFS做出来的 （PS：以后一定要看清题 求得是 最短 最少    一定要用BFS  别用DFS）

Catch That Cow

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 135540		Accepted: 41919

Description

Farmer John has been informed of the location of a fugitive cow and wants to catch her immediately. He starts at a point N (0 ≤ N ≤ 100,000) on a number line and the cow is at a point K (0 ≤ K ≤ 100,000) on the same number line. Farmer John has two modes of transportation: walking and teleporting.

* Walking: FJ can move from any point X to the points X - 1 or X + 1 in a single minute
* Teleporting: FJ can move from any point X to the point 2 × X in a single minute.

If the cow, unaware of its pursuit, does not move at all, how long does it take for Farmer John to retrieve it?

Input

Line 1: Two space-separated integers: N and K

Output

Line 1: The least amount of time, in minutes, it takes for Farmer John to catch the fugitive cow.

Sample Input

5 17

Sample Output

4

Hint

The fastest way for Farmer John to reach the fugitive cow is to move along the following path: 5-10-9-18-17, which takes 4 minutes.

#include<queue>
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define M 1000100
int vis[M];
int n,k;

bool check(int x){
	
	if(x<0 || x>M || vis[x])
	return false;
	return true;
}

struct node
{
	int x;
	int step;
//	node(int xx,int ss){
//		x=xx;
//		step=ss;
//	}
};



int  bfs(int x)  
{ 
	queue<node> q;
	vis[x]=1;
	node a,b;
	a.x=x;
	a.step=0;
	
	q.push(a);	
	while(!q.empty())
	{
		a = q.front();
		q.pop();
		if(a.x == k)  return a.step;
		b.step = 0;
		b.x=a.x-1;
		if(check(b.x) ){
			vis[b.x]=1;
			b.step =a.step+1;
			q.push(b);
		}
		b.x=a.x+1;
		if(check(b.x)){
			vis[b.x]=1;
			b.step =a.step+1;
			q.push(b);
		}
		b.x=a.x*2;
		if(check(b.x)){
			vis[b.x]=1;
			b.step =a.step+1;
			q.push(b);
		}
	  	
	}
	return -1;	
}

int main()
{
	while(scanf("%d%d",&n,&k)!=EOF)
	{
		memset(vis,0,sizeof(vis));
		
		printf("%d\n",bfs(n));
	
	}	
	return 0;
 } 

这道题写的我很气 明明 ‘queue<node> q;’  可以写bfs函数上面  也可以写在bfs函数里面 可是hdu偏偏不行 必须写到bfs函数里面 要么就WA 我找了俩小时 提交了快20次 才知道我错哪儿了

but  poj就行 （滑稽.jpg）