Update baseball-game.py

Author: kamyu104

Python/baseball-game.py

@@ -1,6 +1,49 @@
 # Time:  O(n)
 # Space: O(n)
 
+# You're now a baseball game point recorder.
+# Given a list of strings, each string can be one of the 4 following types:
+#
+# 1. Integer (one round's score): Directly represents the number of points you get in this round.
+# 2. "+" (one round's score): Represents that the points you get in this round are
+#                             the sum of the last two valid round's points.
+# 3. "D" (one round's score): Represents that the points you get in this round are
+#                             the doubled data of the last valid round's points.
+# 4. "C" (an operation, which isn't a round's score): Represents the last valid round's points
+#                              you get were invalid and should be removed.
+#       
+# Each round's operation is permanent and could have an impact on the round before and the round after.
+# You need to return the sum of the points you could get in all the rounds.
+#
+# Example 1:
+#
+# Input: ["5","2","C","D","+"]
+# Output: 30
+# Explanation: 
+# Round 1: You could get 5 points. The sum is: 5.
+# Round 2: You could get 2 points. The sum is: 7.
+# Operation 1: The round 2's data was invalid. The sum is: 5.  
+# Round 3: You could get 10 points (the round 2's data has been removed). The sum is: 15.
+# Round 4: You could get 5 + 10 = 15 points. The sum is: 30.
+#                                 
+# Example 2:
+#
+# Input: ["5","-2","4","C","D","9","+","+"]
+# Output: 27
+# Explanation: 
+# Round 1: You could get 5 points. The sum is: 5.
+# Round 2: You could get -2 points. The sum is: 3.
+# Round 3: You could get 4 points. The sum is: 7.
+# Operation 1: The round 3's data is invalid. The sum is: 3.  
+# Round 4: You could get -4 points (the round 3's data has been removed). The sum is: -1.
+# Round 5: You could get 9 points. The sum is: 8.
+# Round 6: You could get -4 + 9 = 5 points. The sum is 13.
+# Round 7: You could get 9 + 5 = 14 points. The sum is 27.
+#
+# Note:
+# The size of the input list will be between 1 and 1000.
+# Every integer represented in the list will be between -30000 and 30000.
+                                  
 class Solution(object):
     def calPoints(self, ops):
         """