Java:

public static int theLoveLetterMystery(String s) {
    int left = 0;
    int right = s.length() - 1;
    int retVal = 0;
    while (left < right) {
        if (s.charAt(left) != s.charAt(right)) {
            retVal += Math.abs((int) s.charAt(right) - (int) s.charAt(left));
        }
        ++left;
        --right;
    }
    return retVal;
}