门| Gate IT 2008 |问题2

简介

'门| Gate IT 2008 |问题2' 是针对 Gate IT 2008 考试中的问题2的一个程序。

问题描述

问题2要求实现一个程序，该程序对一个给定的表达式进行求值操作。输入的表达式包含了整数、运算符、括号和空格。程序需要按照给定的优先级和结合性规则进行求值，输出表达式的结果。

解决方案

下面是一个简要的解决方案的示例代码，用于实现对给定表达式的求值操作。

def evaluate_expression(expression):
    # Remove whitespace from the expression
    expression = expression.replace(" ", "")

    # Evaluate the expression using a stack and two queues
    operators = []
    operands = []

    for char in expression:
        if char.isdigit():
            operands.append(int(char))
        elif char == "+":
            operators.append(char)
        elif char == "-":
            operators.append(char)
        elif char == "*":
            operators.append(char)
        elif char == "/":
            operators.append(char)
        elif char == "(":
            operators.append(char)
        elif char == ")":
            # Evaluate the expression within the parentheses
            while operators[-1] != "(":
                operand2 = operands.pop()
                operand1 = operands.pop()
                operator = operators.pop()

                result = perform_operation(operator, operand1, operand2)
                operands.append(result)

            operators.pop()  # Remove the "(" symbol

    while operators:
        operand2 = operands.pop()
        operand1 = operands.pop()
        operator = operators.pop()

        result = perform_operation(operator, operand1, operand2)
        operands.append(result)

    return operands[0]


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


# Example usage
expression = "2 + 3 * (4 - 1)"
result = evaluate_expression(expression)
print(result)

结论

'门| Gate IT 2008 |问题2' 是一个求值给定表达式的程序。通过使用栈和队列的数据结构，可以按照给定的规则对表达式进行求值。以上示例代码提供了一个简单的解决方案，但根据实际要求，可能需要进一步修改或扩展该代码。