Postfix Evaluation

 

#include<stdio.h>
#define Maxsize 20

void push(int num);
int pop();
int top=-1;
int stack [Maxsize];

void main()
{      
    char exp[50];
       
    int i=0,op1,op2,result;
     

     printf("Enter the expression:");
     
     gets (exp);
    while(exp[i]!='\0')
    {    
        if (isdigit(exp[i]))        
             push(exp[i]-'0');
             
        else
        {   switch (exp[i])
            {        
            case '+' :
                op2 = pop();
                op1 = pop();
                result = op1+op2;
                break;
                 
             case '-' :
                op2 = pop();
                op1 = pop();
                result= op1-op2;
                 
                break;
            case '*' :
                op2 = pop();
                op1 = pop();
                result = op1*op2;
                break;
             case '/' :
                op2 = pop();
                op1 = pop();
                result = op1/op2;
                break;
                   
            }      
               push (result);
               
             
        }    
        i++;
    }  

    if(top>0)
    {
        printf("error");
    }
    else
    {
        printf("result = %d",pop());
    }
}

void push(int num)
{
    top++;
    stack[top]=num;
}
 
int pop()
{
    int x = stack[top];
    top--;
    return x;
}

     

           

Note: Need to be arranged in compiler after copied

   

 OutPut:

Enter the expression:34+5* result = 35