Question

(9+3)*(8-5)/6*(3+8) in rpn expression in c++

Answer 1

CODE:

#include<iostream>
#include<cctype>
#include<string>
#define MAX 20
using namespace std;
char S[MAX],top=-1;
void push(char ch)      //stack push operation
{
  
   top=top+1;
   S[top]=ch;
}
char pop()           //stack pop operation
{
   if(top==-1)
       return -1;
   else
       return S[top--];
}
int getWeight(char ch)      //method for getting precedence of operator
{
   if(ch=='(')
       return 0;
   if(ch=='-' || ch=='+')
       return 1;
   if(ch== '/' || ch== '*')
       return 2;      
}
int main()
{
   string str;     //declaring string for reading infix expression
   cout<<"Enter expression: ";
   getline(cin,str);    //reading expression from user
   cout<<"RPN expression is:"<<endl;
   for(int i=0;i<str.length();i++)
   {
       if(isalnum(str[i]))   //checking the character is alphanumeric or not
           push(str[i]);     //pushing character to stack
       else if(str[i]=='(') //if character is left paranthesis pushing character to stack
           push(str[i]);
       else if(str[i]==')')
       {
           while((str[i]=pop())!= '(') //poping stack until left paranthesis encountered
            {
               cout<<str[i];     //printing popped characters
           }
       }
       else
        {
           //if top of the stack is having heigher precendence than present operator
            while(getWeight(S[top])>=getWeight(str[i]))
           {
               cout<<pop();   //popping elements until top of the stack have lower presendence
           }   
            push(str[i]);      //pushing character to stack
        }          
   }
   while(top!=-1)    //popping remainging characters and printing them
    {
        cout<<pop();
    }
}

OUTPUT:

Enter expression: (9+3)*(8-5)/6* (3+8) RPN expression is: 93+85-*6/38+*