public String removeDuplicates(String s) { char prevChar = 'A'; StringBuilder stack = new StringBuilder(); for (char c : s.toCharArray()) { int len = stack.length(); if (len > 0 && stack.charAt(len - 1) == c) { stack.deleteCharAt(len - 1); // Remove the duplicate } else { stack.append(c); // Add new character } } return stack.toString(); }