c++ - 评估后缀

Question

我的代码假设计算后缀表达式的值。但我被困在“结果”上，我不知道如何编写代码。我写道:result = operand1 operation.push operand2 逻辑上会报错。我使用了 2 个堆栈。

int main() 
{
    string input;
    cout << "Enter a postfix expression: " << endl;
    getline(cin, input);

    double operand1, operand2, result;
    stack<double> number;
    stack<char>operation;

    int i=0;
    while (i < input.length()) 
    {
        if (input[i] == '+' || input[i] == '-' || input[i] == '*' || input[i] == '/' || input[i] == '^') 
            operation.push(input[i]);
        else 
            number.push(input[i]);
        i++;
    }

    operand2 = number.top( );
    number.pop( );
    operand1 = number.top( );
    number.pop( );
    result = operand1 operation.push(input[i]) operand2
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    return 0;
}

谁能提出更好的解决方案？谢谢

Answer 1

您需要对运算符进行切换并自行计算结果:

char op = operation.top();
switch( op ) {
    case '+': result = operand1 + operand2; break;
    case '-': result = operand1 - operand2; break;
    case '*': result = operand1 * operand2; break;
    case '/': result = operand1 / operand2; break;
    case '^': result = pow(operand1, operand2) ; break;
}