算术表达式求值演示数据结构代码

以下是一个算术表达式求值的演示代码，使用数据结构中的栈来实现：

class Stack:
    def __init__(self):
        self.items = []

    def is_empty(self):
        return len(self.items) == 0

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()

    def peek(self):
        if not self.is_empty():
            return self.items[-1]

    def size(self):
        return len(self.items)


def evaluate_expression(expression):
    operators = {'+': 1, '-': 1, '*': 2, '/': 2}
    operand_stack = Stack()
    operator_stack = Stack()

    for char in expression:
        if char.isdigit():
            operand_stack.push(int(char))
        elif char in operators:
            while (not operator_stack.is_empty() and
                   operators[char] <= operators[operator_stack.peek()]):
                operand2 = operand_stack.pop()
                operand1 = operand_stack.pop()
                operator = operator_stack.pop()
                result = perform_operation(operand1, operand2, operator)
                operand_stack.push(result)
            operator_stack.push(char)

    while not operator_stack.is_empty():
        operand2 = operand_stack.pop()
        operand1 = operand_stack.pop()
        operator = operator_stack.pop()
        result = perform_operation(operand1, operand2, operator)
        operand_stack.push(result)

    return operand_stack.pop()


def perform_operation(operand1, operand2, operator):
    if operator == '+':
        return operand1 + operand2
    elif operator == '-':
        return operand1 - operand2
    elif operator == '*':
        return operand1 * operand2
    elif operator == '/':
        return operand1 / operand2


expression = "3+4*2-6/3"
result = evaluate_expression(expression)
print("Result:", result)  # 输出：7