水题
import numpy as np
def calPoints(ops):
"""
:type ops: List[str]
:rtype: int
"""
nums = []
for op in ops:
if op == '+': nums.append(nums[-1] + nums[-2])
elif op == 'D': nums.append(nums[-1] * 2)
elif op == 'C': nums.pop()
else: nums.append(int(op))
return sum(nums)
# sample:
ops = ["5","2","C","D","+"]
print(calPoints(ops))
ops = ["5","-2","4","C","D","9","+","+"]
print(calPoints(ops))