Baseball Game

import java.util.*;

import static java.lang.Character.isDigit;
import static java.lang.Character.isLetter;

public class BaseballGame {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Queue<String> queue = new LinkedList<>();
        Stack<Integer> stack = new Stack<>();
        String input = scanner.nextLine();

        for (int i = 0; i < input.length(); i++) {
            if(input.charAt(i) == '-'){
                stack.add(-input.charAt(i+1));
                continue;
            }
            if (isDigit(input.charAt(i))) {
                stack.add(Character.getNumericValue(input.charAt(i)));
            }
            if(isLetter(input.charAt(i))){
                if(input.charAt(i) == 'C' || input.charAt(i) == 'D'){
                    queue.offer(Character.toString(input.charAt(i)));
                }
            }
            if(input.charAt(i) == '+'){
                queue.offer(Character.toString(input.charAt(i)));
            }
        }
        while(!queue.isEmpty()) {
            int result = 0;
            if (queue.peek().equals("C")) {
                stack.pop();
                queue.poll();
            }
            if (queue.peek().equals("D")) {
                result = stack.peek() * 2;
                stack.push(result);
                queue.poll();
            }
            if (queue.peek().equals("+")) {
                int temp1 = stack.pop();
                int temp2 = stack.pop();
                result = temp1 + temp2;
                stack.push(temp2);
                stack.push(temp1);
                stack.push(result);
                queue.poll();
            }
        }
        int total = 0;
        for (int n : stack) {
            total += n;
        }
        System.out.println(total);

    }
}


// TODO
//        EXAMPLE 1:
//        Input: ops = ["5","2","C","D","+"]
//        Output: 30
//        Explanation:
//        "5" - Add 5 to the record, record is now [5].
//        "2" - Add 2 to the record, record is now [5, 2].
//        "C" - Invalidate and remove the previous score, record is now [5].
//        "D" - Add 2 * 5 = 10 to the record, record is now [5, 10].
//        "+" - Add 5 + 10 = 15 to the record, record is now [5, 10, 15].
//        The total sum is 5 + 10 + 15 = 30.
//        EXAMPLE 2:
//        Input: ops = ["5","-2","4","C","D","9","+","+"]
//        Output: 27
//        Explanation:
//        "5" - Add 5 to the record, record is now [5].
//        "-2" - Add -2 to the record, record is now [5, -2].
//        "4" - Add 4 to the record, record is now [5, -2, 4].
//        "C" - Invalidate and remove the previous score, record is now [5, -2].
//        "D" - Add 2 * -2 = -4 to the record, record is now [5, -2, -4].
//        "9" - Add 9 to the record, record is now [5, -2, -4, 9].
//        "+" - Add -4 + 9 = 5 to the record, record is now [5, -2, -4, 9, 5].
//        "+" - Add 9 + 5 = 14 to the record, record is now [5, -2, -4, 9, 5, 14].
//        The total sum is 5 + -2 + -4 + 9 + 5 + 14 = 27.
//        EXAMPLE 3:
//        Input: ops = ["1","C"]
//        Output: 0
//        Explanation:
//        "1" - Add 1 to the record, record is now [1].
//        "C" - Invalidate and remove the previous score, record is now [].
//        Since the record is empty, the total sum is 0.
//        Constraints:
//        1 <= operations.length <= 1000
//        operations[i] is "C", "D", "+", or a string representing an integer in the range [-3 * 104, 3 * 104].
//        For operation "+", there will always be at least two previous scores on the record.
//        For operations "C" and "D", there will always be at least one previous score on the record.
//