hdu 2717 从n点走到k点 (BFS)

在横坐标上 从n点走到k点 至少要几步 可以到 n+1 n-1 n*2这3个点

Sample Input
5 17

Sample Output
4

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

 int n , k ;
 int ans ;
 bool v[] ;

 struct node
 {
     int x ;
     int step ;
 };

 bool yes(int x)
 {
     if (x>= && x<=  && v[x] == )
         return  ;
     else
         return  ;
 }

 int bfs()
 {
     queue<node> q ;
     node now , t ;
     now.x = n ;
     now.step =  ;
     q.push(now) ;
     memset(v ,  , sizeof(v)) ;
     v[n] =  ;
     while(!q.empty())
     {
         now = q.front() ;
         q.pop() ;
         if (now.x == k)
             return now.step ;
         t.x = now.x +  ;
         if (yes(t.x))
         {
             t.step = now.step +  ;
             q.push(t) ;
             v[t.x] =  ;
         }
         t.x = now.x -  ;
         if (yes(t.x))
         {
             t.step = now.step +  ;
             q.push(t) ;
             v[t.x] =  ;
         }
         t.x = now.x *  ;
         if (yes(t.x))
         {
             t.step = now.step +  ;
             q.push(t) ;
             v[t.x] =  ;
         }

     }
     return  ;
 }

 int main ()
 {

     while (scanf("%d %d" , &n , &k) != EOF)
     {

         ans = bfs() ;
         printf("%d\n" , ans) ;
     }

     return  ;
 }