python实现利用stack对输入的式子进行计算算法

__author__ = "Alexander Joslin"
import operator as op
from .stack import Stack
def dijkstras_two_stack_algorithm(equation: str) -> int:
    """
    DocTests
    >>> dijkstras_two_stack_algorithm("(5 + 3)")
    8
    >>> dijkstras_two_stack_algorithm("((9 - (2 + 9)) + (8 - 1))")
    5
    >>> dijkstras_two_stack_algorithm("((((3 - 2) - (2 + 3)) + (2 - 4)) + 3)")
    -3

    :param equation: a string
    :return: result: an integer
    """
    operators = {"*": op.mul, "/": op.truediv, "+": op.add, "-": op.sub}

    operand_stack: Stack[int] = Stack()
    operator_stack: Stack[str] = Stack()

    for i in equation:
        if i.isdigit():
            # RULE 1
            operand_stack.push(int(i))
        elif i in operators:
            # RULE 2
            operator_stack.push(i)
        elif i == ")":
            # RULE 4
            opr = operator_stack.peek()
            operator_stack.pop()
            num1 = operand_stack.peek()
            operand_stack.pop()
            num2 = operand_stack.peek()
            operand_stack.pop()

            total = operators[opr](num2, num1)
            operand_stack.push(total)

    # RULE 5
    return operand_stack.peek()


if __name__ == "__main__":
    equation = "(5 + ((4 * 2) * (2 + 3)))"
    # answer = 45
    print(f"{equation} = {dijkstras_two_stack_algorithm(equation)}")