682. Baseball Game

Description

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

You are given a list of strings operations, where operations[i] is the i^th 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.

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 = [“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.

Submitted Code

class Solution(object):
    def calPoints(self, operations):
        """
        :type operations: List[str]
        :rtype: int
        """
        stack = []

        for op in operations:
            if op == "+":
                stack.append(stack[-1] + stack[-2])
            elif op == "D":
                stack.append(stack[-1] * 2)
            elif op == "C":
                stack.pop()
            else:
                stack.append(int(op))

        return sum(stack)

Runtime: 0 ms | Beats 100.00%
Memory: 12.56 MB | Beats 41.90%

+나 C, D를 정수형으로 변환하면 오류가 나기 때문에 앞에서 모두 필터링한 후 숫자일 경우를 else문으로 넣었다.

Other Solutions

1st

class Solution:
    def calPoints(self, operations: List[str]) -> int:
        res = []
        for i in range(len(operations)):
            try:
                res.append(int(operations[i]))
            except ValueError:
                if operations[i] == "+":
                    res.append(res[-2] + res[-1])
                elif operations[i] == "D":
                    res.append(res[-1] * 2)
                elif operations[i] == "C":
                    res.pop()  # pop is way quicker here than del
        return sum(res)

time complexity: 𝑂(𝑛)
space complexity: 𝑂(𝑛)

먼저 try에서 정수형으로 변환을 시도한 후, ValueError가 발생할 경우 except 처리하는 방법도 있었다.