[leetcode]Valid Palindrome

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.

C++ 实现：

#include <string>
#include <iostream>
#include <vector>
using namespace std;
class Solution {
public:
    bool isPalindrome(string s) {
        int length = s.length();
        if(length == 0 || length == 1)return true;
        int i = 0,j = length - 1;
        while(i <= j){
            char prev = s[i];
            char last = s[j];
            bool p = isalpha(prev) || isdigit(prev);
            bool l = isalpha(last) || isdigit(last);
            if( p && l){
                if(tolower(prev) == tolower(last)){
                    ++i;
                    --j;
                    continue;
                }else{
                    return false;
                }
            }
            else if(p)--j;
            else if(l)++i;
            else{--j;++i;}
        }
        return true;
    }
};

int main()
{
    Solution s = Solution();
    cout << s.isPalindrome("1a2") << endl;
    return 1;
}