CareerCup

Any feedback about my performance would be helpful.

I have my (unfinished) answer that I managed to code by the end of the interview. I also have my answer that I coded after the interview was over. Did I miss anything, or is there a simpler answer out there? I feel like I was pretty close, although I didn't finish, which feels pretty bad.

Palindrome question:
Is a string reversible?
Ignore illegal characters; ignore case. Only alphabetic characters are valid.

Here was my answer after ~45 mins:

/*
 * Compare both ends for equality, meeting in the middle
 */

public static boolean isReversible(String s) {
    
    char[] chars = s.toCharArray();
    int back = chars.length - 1;
    int front = 0;
    int middle = chars.length / 2;


    while (front < back) {
        char backChar = chars[back];
        char frontChar = chars[front];
        // check backChar as a alpha char
        while (backChar < ‘a’ || backChar > ‘z’) {
            back--;
            
            if (back < middle)
                return false;
            
            // Double check for multiple non-alpha chars
            middle--;
            backChar = chars[back];
        }
        
        // check frontChar as a alpha char
        while (frontChar < ‘a’ || backChar > ‘z’) {
            front++;
            
            if (front >= middle)
                return false;

            // Double check for multiple non-alphas
            middle++;

            frontChar = chars[front];
        }  

        // We know that frontChar and backChar are both alpha   
        // Check whether front and back are not past the middle
        

        if (frontChar != backChar)
            return false;
        
        front++;
        back--;

    }

    return true;      
}

Here was an answer that I came up with after the interview, which I believe is complete after manual testing:

/*
 * Compare both ends for equality, meeting in the middle
 */

public static boolean isReversible(String s) {
    s = s.toLowerCase();
    char[] chars = s.toCharArray();
    int back = chars.length - 1;
    int front = 0;


    while (front < back) {
        char backChar = chars[back];
        char frontChar = chars[front];
        // check backChar as an alpha char
        while (backChar < 'a' || backChar > 'z') {
            back--;
            
            if (back < front)
                return true;
            
            backChar = chars[back];
        }
        
        // check frontChar as an alpha char
        while (frontChar < 'a' || frontChar > 'z') {
            front++;
            
            if (front > back)
                return true;

            frontChar = chars[front];
        }

        if (frontChar != backChar)
            return false;

        front++;
        back--;

    }

    return true;      
}