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.

本题较为简单，注意使用string提供的函数即可快速解决。值得注意的是字母的大小写问题。直接上代码。

bool isPalindrome(string s)
{
    int len = s.size();
    if(len==0)
        return true;
    for(int i=0,j=len-1;i<j;)
    {
        while( !isalpha(s[i])&& !isdigit(s[i])&& i<j)
            i++;
        while( !isalpha(s[j])&& !isdigit(s[j]) && i<j )
            j--;
        if(i==j)
            return true;
        if( tolower(s[i]) == tolower(s[j]))
        {
            i++;
            j--;
        }
        else
            return false;
    }
    return true;
}