[Python 3] Stack Implementation - Easy.
Approach:\n\nWhen you encounter an integer, typecast it to int() and append to stack. Otherwise,  use if-else conditions to compute value and append the result 
Approach:\n\nWhen you encounter an integer, typecast it to ```int()``` and append to stack. Otherwise,  use ```if-else``` conditions to compute value and append the result to stack. Return ```sum(stack)```.\n```\nclass Solution:\n    def calPoints(self, ops: List[str]) -> int:\n        stack = []\n        for i in ops:\n            if i not in "+DC":\n                stack.append(int(i))\n            else:\n                if i == "C":\n                    stack.pop()\n                elif i == "D":\n                    stack.append(2*stack[-1])\n                elif i == "+":\n                    stack.append((stack[-1]) + stack[-2])\n        return sum(stack)\n```
['Stack', 'Python3']