1544 Make The String Great

1544 Make The String Great.java

class Solution {
    public String makeGood(String s) {
        Stack<Character> st = new Stack<Character>();
        StringBuilder res = new StringBuilder();
        for (char c : s.toCharArray()) {
            if (!st.isEmpty() && Math.abs(st.peek() - c) == 32) {
                st.pop();
            } else {
                st.push(c);
            }
        }
        while (!st.isEmpty()) res.append(st.pop());
        return res.reverse().toString();
    }
}