Practical Name : Write a program to accept a postfix expression and evaluate the expression using the stack.
#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;
}