我无法搞清楚RPN计算器，我们必须使用链接列表进行此分配。 （我已使用stack<double>方法完成了作业，但它必须使用链接列表。
我在错误检查方面遇到了一些问题：
操作员太多（+ - / *） 操作数太多（双打） 除以零
程序应该继续采用和计算表达式，直到用户在一行上输入零（0）后跟一个新行。我也遇到了一些麻烦。因为我把我的错误检查“太多操作数”，所以 我不会允许我进行第二次计算，输出将是“太多的操作”
我似乎无法对“太多操作员”进行错误检查
我已经针对所需的错误检查尝试了几种不同的东西，并查看了不同站点上的许多其他RPN问题，因为您可以看到我尝试过并注释掉的一些内容。 任何帮助将不胜感激！ 感谢
#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
using namespace std;
struct NODE
{
float num;
NODE *next;
};
class stack
{
private:
NODE *head;
public:
stack();
void push(float);
float pop();
int nElements();
float display();
};
class RPN: public stack
{
public:
void add();
void subtract();
void multiply();
void divide();
};
stack::stack()
{
head = NULL;
}
void stack::push(float a_number)
{
NODE *temp = new NODE;
if (temp)
{
temp->num = a_number;
temp->next = head;
head = temp;
}
}
float stack::pop()
{
float number = 0;
if (!head)
{
return 0;
}
else
{
NODE *temp = head;
number = head->num;
head = temp->next;
delete temp;
}
return number;
}
int stack::nElements()
{
int counter=0;
for (NODE *node = head; node; node=node->next)
{
counter++;
}
return counter;
}
float stack::display()
{
//ERROR CHECKING TOO MANY OPERANDS??? PRINTING TOO MANY OPERANDS FOR : 100 10 50 25 / * - -2 / = , but still giving correct output && WILL NOT ALLOW ME TO DO A SECOND CALCULATAION , OUTPUT WILL BE TOO MANY OPERANDS
if(nElements() !=1)
{
cout << "Error: too many operands" << endl;
return 1;
}
/*
// if( nElements() < 2 )
{
cout << "Error: too many operators" << endl;
return 1;
}
*/
else //(nElements() > 0)
{
float temp = pop();
cout << temp << endl;
push(temp);
return temp;
}
}
void RPN::add()
{
if (nElements()>=2)
{
push(pop() + pop());
}
}
void RPN::subtract()
{
if (nElements()>=2)
{
push(0 - pop() + pop());
}
}
void RPN::multiply()
{
if (nElements()>=2)
{
push(pop() * pop());
}
}
int RPN::divide()
{
double op2;
op2 = pop();
if(op2 != 0.0)
{
push(pop() / op2);
}
else
{
cout << "Error: Division by zero.\n"; //??? Still printing output
return -1;
}
}
//Function prototype for isOperator
bool isOperator(const string& input);
//Function prototype for perforOperation
int performOperation(const string& input, RPN& calculator);
Int main(){
RPN calculator;
string input;
float num;
cout << "RPN Calculator: " << endl;
cout << "Input\n";
while(input != "0")
{
//Terminate program when 0 is entered by user
while(true)
{
// get input
cin >> input;
// check for being numeric value
if(istringstream(input) >> num)
{
//use push function
calculator.push(num);
}
// check for operator
else if(isOperator(input))
{
performOperation(input, calculator);
}
// If user enters 0 on a line followed by a new line, the program exits ????????????
else if(input == "0\n")
{
return -1;
}
}
}
}
bool isOperator(const string& input)
{
static const string operators ="-+*/";
if (input.length() == 1) // right size to be an operator.
{
return operators.find_first_of(input[0]) != string::npos;
// look in the operator string for the first (and only) character in input
}
return false;
}
int performOperation(const string& input, RPN& calculator)
{
//double firstOperand = 0;
//double secondOperand = 0;
//double result;
/*
if( calculator.size() > 2 ) //Error check gives a false error for last input ???
{
cout << "Error: too many operands" << endl;
return 1;
}
//Error chceck for too many operators ////STILL PRINT OUTPUT???
if( calculator.size() < 2 )
{
cout << "Error: too many operators" << endl;
return 1;
}
*/
switch (input[0])
{
case '+': calculator.add();
calculator.display();
break;
case '-': calculator.subtract();
calculator.display();
break;
case '*': calculator.multiply();
calculator.display();
break;
case '/': calculator.divide();
//if (firstOperand / 0)
//{
// cout << "Error: Divide by 0.\n";
//}
calculator.display();
break;
}
/*
if (secondOperand == 0)
{ // moved this test to here because it's the only place it matters.
cout << "Error: Division by 0.\n";
return -1;
}
*/
return 0;
}
This is the sample input and output
Input Output
10 15 + = 25
10 15 - = -5
2.5 3.5 + = 6 (or 6.0)
10 0 / = Error: Division by zero
10 20 * / = Error: Too many operators
12 20 30 / = Error: Too many operands
-10 -30 - = 20
100 10 50 25 / * - -2 / = -40
I got the error division by 0 check to work, It just keeps printing the output in addition to the error...How could I fix this?
int RPN::divide()
{
double op2;
op2 = pop();
if(op2 != 0.0)
{
push(pop() / op2);
}
else
{
cout << "Error: Division by zero.\n";
return -1;
}
}
答案 0 :(得分：0)
问题是你总是将计算结果留在堆栈上。因此，当您进行第二次计算时，您不会以空堆栈开始。简单的解决方法是在stack::display()
push(temp);
也可以将stack::display()重命名为stack::display_and_pop()。