leetcode-125-valid palindrome

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.

给定一个字符串，判断它是否是回文的。

这道题不难，只要对原始字符串进行适当的预处理之后（去掉标点符号）在判断是否是回文即可。

class Solution {
public:
    bool isPalindrome(string s) {
        string nstr="";
        for(int i = 0; i < s.length(); i++)
        {
            if(s[i]>='a'&&s[i]<='z')
                nstr+=s[i];
            else if(s[i]>='A'&&s[i]<='Z')
                nstr+=(char)(s[i]-'A'+'a');
            else if(s[i]>='0'&&s[i]<='9')
                nstr+=s[i];
        }
        for(int i = 0;i<nstr.length();i++)
        {
            if(nstr[i]!=nstr[nstr.length()-1-i]) return false;
        }
        return true;

    }
};