682. Baseball Game

Difficulty: Easy
39 / 39 test cases passed.
Runtime: 36 ms
Memory Usage: 14.1 MB

Author: YuriSpiridonov

Easy/682.BaseballGame.py

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+"""
+    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.
+
+    At the beginning of the game, you start with an empty record. You are given 
+    a list of strings ops, where ops[i] is the ith operation you must apply to 
+    the record and is one of the following:
+        1. An integer x - Record a new score of x.
+        2. "+" - Record a new score that is the sum of the previous two scores. 
+           It is guaranteed there will always be two previous scores.
+        3. "D" - Record a new score that is double the previous score. It is 
+           guaranteed there will always be a previous score.
+        4. "C" - Invalidate the previous score, removing it from the record. 
+           It is guaranteed there will always be a previous score.
+
+    Return the sum of all the scores on the record.
+
+    Example:
+    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:
+    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:
+    Input: ops = ["1"]
+    Output: 1
+
+    Constraints:
+        - 1 <= ops.length <= 1000
+        - ops[i] is "C", "D", "+", or a string representing an integer in the 
+          range [-3 * 10**4, 3 * 10**4].
+        - 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.
+"""
+#Difficulty: Easy
+#39 / 39 test cases passed.
+#Runtime: 36 ms
+#Memory Usage: 14.1 MB
+
+#Runtime: 36 ms, faster than 85.56% of Python3 online submissions for Baseball Game.
+#Memory Usage: 14.1 MB, less than 100.00% of Python3 online submissions for Baseball Game.
+
+class Solution:
+    def calPoints(self, ops: List[str]) -> int:
+        scores = []
+        for n in ops:
+            if n == "+":
+                scores.append(scores[-1] + scores[-2])
+            elif n == "D":
+                scores.append(scores[-1] * 2)
+            elif n == "C":
+                scores.pop()
+            else:
+                scores.append(int(n))
+        return sum(scores)