772. Basic Calculator III

772. Basic Calculator III

前面兩題解完，此題題目有變化，答案無變化

class Solution:
    def calculate(self, s: str) -> int:
        def helper(s):
            num = 0
            stack = []
            sign = '+'
            while s:
                c = s.popleft()
                if c.isdigit():
                    num = 10 * num + int(c)
                if c == '(':
                    num = helper(s)
                if c in '+-*/' or len(s) == 0:
                    if sign == '+':
                        stack.append(num)
                    elif sign == '-':
                        stack.append(-num)
                    elif sign == '*':
                        stack.append(stack.pop() * num)
                    elif sign == '/':
                        stack.append(int(stack.pop() / num))
                    sign = c
                    num = 0
                if c == ')': break
            return sum(stack)
        return helper(deque(list(s)))