leetcode--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.

#include<iostream>
#include<string.h>
using namespace std;
bool isPalindrome(string s) 
{
    string temp;
    if(s.length() == 0 || s.length() == 1)
        return 1;
        for(int i = 0;i<s.length();i++)
        {
            if(s[i]>='a' && s[i]<='z')
            {
                temp += s[i];
            }
            else if(s[i] >= 'A' && s[i] <= 'Z')
            {
                temp += (char)((int)s[i]+32);
            }
            else if(s[i]>='0' && s[i]<='9')
            {
                temp += s[i];
            }
        }
        int low = 0;
        int high = temp.length()-1;
        bool result = true;
        if(temp.length()==0 || temp.length()==1)
            return 1;
        while(low < high)
        {
            if(temp[low] != temp[high])
            {
                result = false;
                return result;
            }
            else 
            {
                low ++;
                high --;
            }
        }
        return result;
}


int main()
{
    //string s = "a.";
    cout << isPalindrome(s) << endl;
    system("pause");
    
    return 0;

}