leetcode - Valid Palindrome

 

class Solution {
public:
    int getNum(char c){
    if (c>='a' && c<='z')
        return c-'a';
    if (c>='A' && c<= 'Z')
        return c-'A';
    if (c>='0' && c<='9')
        return 30 + (c-'0');
    return -1;
    }
    bool isPalindrome(string s) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int len = s.length();
    int i =0, j = len-1;
    while (i<j && i<len && j>=0){
        char x = s.at(i);
        int a = getNum(x);
        if (a==-1){
        i++;
        continue;
        }
        char y = s.at(j);
        int b = getNum(y);
        if (b==-1){
        j--;
        continue;
        }
        if (a!=b)
        return false;
        i++;
        j--;
    }
    return true;
    }
};