HDU 1548 (最基础的BFS了) A strange lift

 1 //#define LOCAL
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 const int maxn = 200 + 10;
 8 struct Point
 9 {
10     int h;
11     int times;
12 }qu[maxn];
13 int n, from, to, go[maxn], vis[maxn];
14 int head, tail;
15 int dir[2] = {1, -1};
16 
17 void BFS(void)
18 {
19     head = 0, tail = 1;
20     qu[0].h = from, qu[0].times = 0;
21     while(head < tail)
22     {
23         if(qu[head].h == to)
24         {
25             printf("%d\n", qu[head].times);
26             return;
27         }
28         for(int i = 0; i < 2; ++i)
29         {
30             int hh = qu[head].h + go[qu[head].h]*dir[i];
31             if(hh>0 && hh<=n && (!vis[hh]))
32             {
33                 vis[hh] = 1;
34                 qu[tail].h = hh;
35                 qu[tail++].times = qu[head].times + 1;
36             }
37         }
38         ++head;
39     }
40     printf("-1\n");
41 }
42 
43 int main(void)
44 {
45     #ifdef LOCAL
46         freopen("1548in.txt", "r", stdin);
47     #endif
48 
49     while(scanf("%d", &n) == 1 && n)
50     {
51         scanf("%d%d", &from, &to);
52         for(int i = 1; i <= n; ++i)
53             scanf("%d", &go[i]);
54         memset(vis, 0, sizeof(vis));
55         BFS();
56     }
57     return 0;
58 }