LeetCode(125)题解--Valid Palindrome

https://leetcode.com/problems/valid-palindrome/

题目：

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：

easy.

AC代码：

class Solution {
public:
    bool isPalindrome(string s) {
        int a=0,b=s.size()-1;
        while(a<b){
            if(!((s[a]>='a'&&s[a]<='z')||(s[a]>='A'&&s[a]<='Z')||(s[a]>='0'&&s[a]<='9'))){
                a++;
                continue;
            }
            if(!((s[b]>='a'&&s[b]<='z')||(s[b]>='A'&&s[b]<='Z')||(s[b]>='0'&&s[b]<='9'))){
                b--;
                continue;
            }
            if((s[a]>='a'&&s[a]<='z')){
                if((s[a]!=s[b])&&(s[a]+'A'-'a'!=s[b])){
                    return false;
                }
            }
            else if((s[a]>='A'&&s[a]<='Z')){
                if((s[a]!=s[b])&&(s[a]!=s[b]+'A'-'a')){
                    return false;
                }
            }
            else{
                if(s[a]!=s[b]){
                    return false;
                }
            }
            a++;
            b--;
        }
        return true;
    }
};