HDU 2717 Catch That Cow

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2717

思路：简单的bfs搜索，每个位置只有三个方向

#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
#define N 100001
bool s[N];
struct node
{
    int x,time;
};
bool limit(int x)
{
   if(x>=0&&x<=100000)
	   return true;
   else return false;
}
void bfs(int n,int k)
{
   queue<node> q;
   node a,b;
   memset(s,false,sizeof(s));
   a.x=n;a.time=0;
   s[n]=true;
   q.push(a);
   while(!q.empty())
   {
	   a=q.front();
	   q.pop();
	   if(a.x==k)
	   {
	     printf("%d\n",a.time);
		 return;
	   }
	   if(limit(a.x*2)&&!s[a.x*2])
	   {
	      b.x=a.x*2;b.time=a.time+1;
		  s[a.x*2]=true;
		  q.push(b);
	   }
	   if(limit(a.x-1)&&!s[a.x-1])
	   {
	      b.x=a.x-1;b.time=a.time+1;
		  s[a.x-1]=true;
		  q.push(b);
	   }
	   if(limit(a.x+1)&&!s[a.x+1])
	   {
	      b.x=a.x+1;b.time=a.time+1;
		  s[a.x+1]=true;
		  q.push(b);
	   }
   }
}
int main()
{
   int n,k;
   while(scanf("%d%d",&n,&k)!=EOF)
   {
      if(n>=k)
		  printf("%d\n",n-k);//当k小于n时，只能往左移动位置
	  else 
		 bfs(n,k);
    
   }
  return 0;
}