栈

 1 #include 
 2 #include <string.h>
 3 int  main() {
 4     char a[101], s[101];
 5     int i, len, mid, next, top;
 6 
 7     gets(a); //读入一行字符串
 8     len = strlen(a); //求字符串的长度
 9     printf("%d\n", len);
10     mid = len/2-1; //求字符串的中点
11     printf("%d\n", mid);
12 
13     top = 0; //栈的初始化
14     //将mid前的字符依次入栈
15     for (i = 0; i <= mid; i++)
16         s[++top] = a[i];
17 
18     //判断字符串的长度是奇数还是偶数，并找出需要进行字符匹配的起始下标
19     if (len%2 == 0)
20         next = mid+1;
21     else
22         next = mid+2;
23 
24     //开始匹配
25     for (i = next; i <= len-1; i++) {
26         if (a[i] != s[top])
27             break;
28         top--;
29     }
30 
31     //如果top的值为0，则说明栈内所有的字符都被一一匹配了
32     if (top == 0)
33         printf("YES");
34     else
35         printf("NO");
36 
37     return 0;
38 }