Valid Palindrome (C++ code)

LeetCode Valid Palindrome ,Jan 13

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example, "A man, a plan, a canal: Panama" is a palindrome. "race a car" is not a palindrome. Note: Have you consider that the string might be empty? This is a good question to ask during an interview. For the purpose of this problem, we define empty string as valid palindrome.

思路：继续捏软柿子。。这题唯一要注意的是跳过非字母数字的字符的时候，别忘了同时满足边界条件。

0. bool isPalindrome(string s) {  
1.   
2.        if(s.empty()) return true;  
3.        int start = 0, end = s.length() - 1;  
4.        while(start < end){  
5.   
6.           if(!isalnum(s[start])) {start++; continue;}  
7.   
8.           if(!isalnum(s[end])) {end--; continue;}  
9.   
10.           if(abs(s[start] - s[end]) != 0 && abs(s[start] - s[end]) != 32)  
11.   
12.             return false;  
13.   
14.          else{  
15.   
16.             start++; end--;  
17.   
18.          }  
19.   
20.        }  
21.   
22.     return true;  
23.   
24. }