bfs A strange lift

 1 #include<iostream>
 2 #include<queue>
 3 
 4 using namespace std;
 5 
 6 int k[210],flag[210];
 7 int n,a,b;
 8 
 9 struct node{
10     int floor;
11     int step;
12 };
13 
14 int bfs(){
15     node cur,next;
16     queue<node> q;
17     cur.floor = a;
18     cur.step = 0;
19     flag[a] = 1;//最开始把这个给忘记了还WA了一次，我傻！
20     q.push(cur);
21     while(!q.empty()){
22         cur = q.front();
23         q.pop();
24         if(cur.floor == b){
25             return cur.step;
26         }
27         if(cur.floor+k[cur.floor]<=n && cur.floor+k[cur.floor]>0 && !flag[cur.floor+k[cur.floor]]){
28             next.floor = cur.floor + k[cur.floor];
29             flag[cur.floor] = 1;
30             next.step = cur.step + 1;
31             q.push(next);
32         }
33         if(cur.floor-k[cur.floor]>0 && cur.floor-k[cur.floor]<=n && !flag[cur.floor-k[cur.floor]]){
34             next.floor = cur.floor - k[cur.floor];
35             flag[cur.floor] = 1;
36             next.step = cur.step + 1;
37             q.push(next);
38         }
39     }
40     return -1;
41 }
42 
43 int main(){
44     while(cin>>n,n){
45         cin>>a>>b;
46         for(int i=1;i<=n;i++){
47             cin>>k[i];
48             flag[i]=0;
49         }
50         cout<<bfs()<<endl;
51     }
52     return 0;
53 }