class Solution {
    public String reverseWords(String s) {
        int n = s.length();
        StringBuilder ans = new StringBuilder(n);
        for (int i = n - 1; i >= 0; i--) {
            int j = i;
            StringBuilder x = new StringBuilder();
            while (j >= 0 && s.charAt(j) != ' ') {
                x.append(s.charAt(j--));
            }
            ans.append(x.reverse().toString());
            i = j;
            if (i > 0) {
                ans.append(" ");
            }
        }
        return ans.toString();
    }
}