Question

REVERSE POLISH CALCULATOR

C++ ONLY.

For this assignment, you are to write a program, which will calculate the results of Reverse Polish expressions that are provided by the user.

You must use a linked list to maintain the stack for this program (NO array implementations of the stack).

You must handle the following situations (errors):
Too many operators (+ - / *)
Too many operands (doubles)
Division by zero

The program will take in a Polish expression that separates the operators and operands by a single space, and terminates the expression with an equals sign.

The program will continue to take and evaluate expressions until the user enters a zero (0) on a line by itself followed by a new line.

Your sample output should show the handling of all the error conditions as well as make use of all of the operators.

Sample IO: (note: formatting of output isn’t a critical issue)
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

Thanks. Will rate if solution is correct.

Answer 1

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <algorithm>
#include <iterator>
#include <sstream>
#include <stdlib.h>
#include <ctype.h>
#include<string>
using namespace std;
struct stack//linked list for stack
{
   double data;
   struct stack *next;
};
struct stack *head,*top;

void push(double d)//pushing to stack...//operand stack
{
   if(head==NULL)
   {
       head = new stack();  
       head->data = d;
       head->next =NULL;
       top = head;
   }
   else
   {
       top->next = new stack();
       top->next->data =d;
       top=top->next;  
   }
  
}
int stack_length()//finding number of elements in stack
{
   struct stack *temp =head;
   int i=0;
   while(temp!=NULL)
   {
       i++;
       temp = temp->next;  
   }
   return i;
  
}
double pop()//poping element from stack
{
   double d;
   struct stack *temp=head;
   if(head==NULL)
   {
       cout<<"\nstack is empty\n";
       exit(0);
   }
   if(head==top)
   {
       d=head->data;
       head =NULL;
       top = NULL;  
   }
   else
   {
   while(temp->next != top)
   {
       temp=temp->next;  
   }
   d=top->data;
   temp->next =NULL;
   top=temp;
   }
   return d;
}

//spliting given string at spaces
void split(const std::string& str, std::vector<std::string>& v) {
std::stringstream ss(str);
ss >> std::noskipws;
std::string field;
char ws_delim;
while(1) {
    if( ss >> field )
      v.push_back(field);
    else if (ss.eof())
      break;
    else
      v.push_back(std::string());
    ss.clear();
    ss >> ws_delim;
}
}

bool is_digit(string a)//finding whether digit or not..
{
  
   bool isNumber = true;
   int i;
   for(i=0;a[i]!='\0';i++)
   if(a[i]!='.')if(!isdigit(a[i])){
   isNumber=false;
   break;
   }
  
    return isNumber;
}

bool evaluate(string e)//evaluating expression
{
   if(stack_length()>=2)
   {
       double p1,p2;
       if(e=="+")
       {
           p1=pop();
           p2=pop();
           push(p1+p2);
          
       }
       else if(e=="-")
       {
           p1=pop();
           p2=pop();
           push(p2-p1);
       }
       else if(e=="/")
       {
           p1=pop();
           p2=pop();
           if(p1==0)
           {
               cout<<"Error:Division by zero\n";
               exit(0);
               return true;
           }
           push(p2/p1);  
       }
       else
       {
           p1=pop();
           p2=pop();
           push(p1*p2);
          
       }
      
      
          
   }
   else
   {
       if(e=="=")return false;
       cout<<"Error:Too many operators";
       exit(0);
       return true;  
   }
   return false;
  
}
int main()
{
   string s;
   cout<<"Enter:";
   getline(cin,s);
   vector<string> e;
   split(s,e);
  
  
   int i=0;
   int d;
  
   while(i<e.size())
   {
       //cout<<e[i]<<"\n";
      
       if(is_digit(e[i]))
       {
              push(atof(e[i].c_str()));
       }
       else
       {
           if(evaluate(e[i]))
           {
               break;  
           }
              
       }  
       i++;
   }
  
   if(stack_length()==1)cout<<pop()<<endl;
   else cout<<"Error: Too many operands\n";
   main();
   return 0;
}

ouput