Question

Use stack to evaluate postfix expressions :

5 4 2 1 + 6 * + 3 + *

Answer 1

Lets use simple C Programming

CODE:

#include<stdio.h>
int stack[20];
int top = -1;
void push(int x){
   stack[++top] = x;
}
int pop(){
return stack[top--];
}
int main(){
char exp[20];
char *e;
int n1,n2,n3,num;
printf("Enter the expression :: ");
scanf("%s",exp);
e = exp;
while(*e != '\0'){
if(isdigit(*e)){
num = *e - 48;
push(num);
}
else{
n1 = pop();
n2 = pop();
switch(*e){
   case '+':{
   n3 = n1 + n2;
   break;
   }
   case '-':{
   n3 = n2 - n1;
   break;
   }
   case '*':{
   n3 = n1 * n2;
   break;
   }
   case '/':{
   n3 = n2 / n1;
   break;
   }
}
push(n3);
}
e++;
}
printf("\nThe result of expression %s = %d\n\n",exp,pop());
return 0;
}

SCREENSHOT OF THE CODE:

OUTPUT:

Thank you. Please ask me if you have any doubt.