Programming problem: Baseball Game

Question

You are keeping the scores for a baseball game with strange rules. At the beginning of the game, you start with an empty record.

Given a list of strings operations, where operations[i] is the ith operation you must apply to the record and is one of the following:

• An integer x: Record a new score of x.
• '+': Record a new score that is the sum of the previous two scores.
• 'D': Record a new score that is the double of the previous score.
• 'C': Invalidate the previous score, removing it from the record.

Return the sum of all the scores on the record after applying all the operations.

Note: The test cases are generated such that the answer and all intermediate calculations fit in a 32-bit integer and that all operations are valid.

Example 1

Input: ops = ["1","2","+","C","5","D"]

Output: 18

Explanation:

• "1" - Add 1 to the record, record = [1].
• "2" - Add 2 to the record, record = [1, 2].
• "+" - Add 1 + 2 = 3 to the record, record = [1, 2, 3].
• "C" - Invalidate and remove the previous score, record = [1, 2].
• "5" - Add 5 to the record, record = [1, 2, 5].
• "D" - Add 5 * 2 = 10 to the record, record = [1, 2, 5, 10].
• The total sum is 1 + 2 + 5 + 10 = 18.

Example 2

Input: ops = ["5","D","+","C"]

Output: 15

Explanation:

• "5" - Add 5 to the record, record = [5].
• "D" - Add 5 * 2 = 10 to the record, record = [5, 10].
• "+" - Add 5 + 10 = 15 to the record, record = [5, 10, 15].
• "C" - Invalidate and remove the previous score, record = [5, 10].
• The total sum is 5 + 10 = 15.

Constraints

• 1 <= operations.length <= 1000
• operations[i] is "C", "D", "+", or a string representing an integer in the range [-30,000, 30,000].
• 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.

Solution

function calPoints(operations: string[]): number {
  const record: number[] = [];

  for (const operation of operations) {
    switch (operation) {
      case "+":
        record.push(record[record.length - 1] + record[record.length - 2]);
        break;

      case "C":
        record.pop();
        break;

      case "D":
        record.push(2 * record[record.length - 1]);
        break;

      default:
        record.push(parseInt(operation));
        break;
    }
  }

  return record.reduce((sum, score) => sum + score, 0);
}