POJ2013 Symmetric Order

　　//找规律实现
 1 #include<iostream>
 2 #include<string>
 3 
 4 using namespace std;
 5 
 6 const int maxn=20;
 7 
 8 int main()
 9 {
10     int n;
11     string a[maxn];
12     int cnt=0;
13     while(cin>>n&&n)
14     {
15         cnt++;
16         cout<<"SET "<<cnt<<endl;
17         for(int i=1;i<=n;i++)
18         {
19             cin>>a[i];
20         }
21         
22         if(n>1&&n%2!=0)
23         { 
24             for(int i=1;i<=n;i+=2)
25             {
26                 cout<<a[i]<<endl;
27             }
28             for(int i=n-1;i>=2;i-=2)//seg fault
29             {
30                 cout<<a[i]<<endl;
31             }
32         }
33         else
34         {
35             for(int i=1;i<=n;i+=2)
36             {
37                 cout<<a[i]<<endl;
38             }
39             for(int i=n;i>=2;i-=2)//seg fault: cause by underflow of array
40             {
41                 cout<<a[i]<<endl;
42             }
43         }
44     }
45     return 0;
46 }