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 ith operation you must apply to the record and is one of the following:
- An integer
x.<ul> <li>Record a new score of <code>x</code>.</li> </ul> </li> <li><code>'+'</code>. <ul> <li>Record a new score that is the sum of the previous two scores.</li> </ul> </li> <li><code>'D'</code>. <ul> <li>Record a new score that is the double of the previous score.</li> </ul> </li> <li><code>'C'</code>. <ul> <li>Invalidate the previous score, removing it from the record.</li> </ul> </li>
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 <= 1000operations[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.
Solution
Python3
class Solution:
def calPoints(self, ops: List[str]) -> int:
stack = []
for x in ops:
if x == "C":
stack.pop()
elif x == "D":
stack.append(stack[-1] * 2)
elif x == "+":
stack.append(stack[-1] + stack[-2])
else:
stack.append(int(x))
return sum(stack)