<p>You are keeping score for a baseball game with strange rules. The game consists of several rounds, where the scores of past rounds may affect future rounds' scores.</p> <p>At the beginning of the game, you start with an empty record. You are given a list of strings <code>ops</code>, where <code>ops[i]</code> is the <code>i<sup>th</sup></code> operation you must apply to the record and is one of the following:</p> <ol> <li>An integer <code>x</code> - Record a new score of <code>x</code>.</li> <li><code>"+"</code> - Record a new score that is the sum of the previous two scores. It is guaranteed there will always be two previous scores.</li> <li><code>"D"</code> - Record a new score that is double the previous score. It is guaranteed there will always be a previous score.</li> <li><code>"C"</code> - Invalidate the previous score, removing it from the record. It is guaranteed there will always be a previous score.</li> </ol> <p>Return <em>the sum of all the scores on the record</em>. The test cases are generated so that the answer fits in a 32-bit integer.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> ops = ["5","2","C","D","+"] <strong>Output:</strong> 30 <strong>Explanation:</strong> "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. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> ops = ["5","-2","4","C","D","9","+","+"] <strong>Output:</strong> 27 <strong>Explanation:</strong> "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. </pre> <p><strong>Example 3:</strong></p> <pre> <strong>Input:</strong> ops = ["1"] <strong>Output:</strong> 1 </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= ops.length <= 1000</code></li> <li><code>ops[i]</code> is <code>"C"</code>, <code>"D"</code>, <code>"+"</code>, or a string representing an integer in the range <code>[-3 * 10<sup>4</sup>, 3 * 10<sup>4</sup>]</code>.</li> <li>For operation <code>"+"</code>, there will always be at least two previous scores on the record.</li> <li>For operations <code>"C"</code> and <code>"D"</code>, there will always be at least one previous score on the record.</li> </ul>