LeetCode – Refresh – Valid Palindrome

 1 class Solution {
 2 public:
 3     string preProcess(string s) {
 4         string result;
 5         for (int i = 0; i < s.size(); i++) {
 6             if ((s[i] >= ‘a‘ && s[i] <= ‘z‘) ||
 7                 (s[i] >= ‘0‘ && s[i] <= ‘9‘)) {
 8                 result += s[i];    
 9             } else if (s[i] >= ‘A‘ && s[i] <= ‘Z‘) {
10                 result += s[i] - ‘A‘ + ‘a‘;
11             }
12         }
13         return result;
14     }
15     bool isPalindrome(string s) {
16         s = preProcess(s);
17         int start = 0, end = s.size()-1;
18         while(start < end) {
19             if (s[start++] != s[end--]) return false;
20         }
21         return true;
22     }
23 };