C - Catch That Cow POJ - 3278

 //标准bfs
 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cmath>
 #include <queue>

 using namespace std;

 int dir[] = { , - };

 struct node
 {
     int x, step;
 } s, ss;

 int bfs(int n, int k)
 {
     queue<node>q, qq;
     s.x = n;
     s.step = ;
     int vis[] = {  };
     q.push(s);
     while (!q.empty())
     {
         s = q.front();
         q.pop();
         if (s.x == k)
             return s.step;
         for (int i = ; i < ; i++)
         {
             ss.x = s.x + dir[i];
             ss.step = s.step + ;
             if (ss.x >=  && ss.x <= )
             if (!vis[ss.x])
             {
                 vis[ss.x] = ;
                 q.push(ss);
             }
         }
         ss.x = s.x * ;
         ss.step = s.step + ;
         if (ss.x >=  && ss.x <= )
         {
             if (!vis[ss.x])
             {
                 vis[ss.x] = ;
                 q.push(ss);
             }
         }
     }
     return ;
 }

 int main()
 {
     int n, k;
     while (~scanf("%d%d", &n, &k))
     {
         printf("%d\n", bfs(n, k));
     }
     return ;
 }