class Solution {
    public String reverseWords(String s) {
        StringBuilder sb = new StringBuilder();
        int end = s.length() - 1;
        while (end >= 0) {
            if (s.charAt(end) == ' ') {
                end -= 1;
                continue;
            }

            int start = end - 1;

            while (start >= 0 && s.charAt(start) != ' ') {
                start -= 1;
            }
            sb.append(" ");
            sb.append(s.substring(start + 1, end + 1));
            end = start - 1;
        }
        if (sb.length() > 0) {
            sb.deleteCharAt(0);
        }
        return sb.toString();

    }
}

class Solution {
    public boolean isPalindrome(String s) {
        int left = 0;
        int right = s.length() - 1;

        while (left < right) {
            while (left < right && !Character.isLetterOrDigit(s.charAt(left))) {
                left += 1;
            }

            while (left < right && !Character.isLetterOrDigit(s.charAt(right))) {
                right -= 1;
            }

            char leftChar = Character.toLowerCase(s.charAt(left));
            char rightChar = Character.toLowerCase(s.charAt(right));
            if (leftChar != rightChar) {
                return false;
            }

            left += 1;
            right -= 1;
        }

        return true;
    }
}