BFS/poj 3278 Catch That Cow

 1 #include<cstdio>
 2 #include<queue>
 3 #include<cstring>
 4 using namespace std;
 5 const int MAXN=200010;
 6 int n,k;
 7 bool v[MAXN];
 8 struct point
 9 {
10     int x;
11     int step;
12 };
13 int bfs()
14 {
15     memset(v,0,sizeof(v));
16     queue<point>que;
17     point now,next;
18     now.x=n;
19     now.step=0;
20     v[n]=1;
21     que.push(now);
22 
23     while (!que.empty())
24     {
25         now=que.front();
26         que.pop();
27         if (now.x==k) break;
28 
29         next.x=now.x+1;
30         if (next.x>=0 && next.x<=MAXN && !v[next.x])
31         {
32             v[next.x]=1;
33             next.step=now.step+1;
34             que.push(next);
35         }
36 
37         next.x=now.x-1;
38         if (next.x>=0 && next.x<=MAXN && !v[next.x])
39         {
40             v[next.x]=1;
41             next.step=now.step+1;
42             que.push(next);
43         }
44 
45         next.x=now.x*2;
46         if (next.x>=0 && next.x<=MAXN && !v[next.x])
47         {
48             v[next.x]=1;
49             next.step=now.step+1;
50             que.push(next);
51         }
52 
53     }
54     return now.step;
55 }
56 
57 int main()
58 {
59     while (scanf("%d%d",&n,&k)!=EOF)
60     {
61         printf("%d\n",bfs());
62     }
63     return 0;
64 }