Question

Consider the following C program:

# include <stdio.h>
# define EOF - 1
void push (int); /* push the argument on the stack */
int pop (void); /* pop the top of the stack*/
void flag Error( );
int main ( )
{
int c, m, n, r;
while ((c = getchar ( ))! = EOF)
{
if (isdigit (c))
push (c);
else if ((c = = '+') | | (c = = '*'))
{
m = pop ( );
n = pop ( );
r = (c = = '+') n + m : n*m;
push (r);
}
else if ( c! = ' ')
flag Error ( );
}
printf("%c", pop( ));
}

What is the output of the program for the following input?

5 2 * 3 3 2 + * +

• A. 25
• B. 150
• C. 30
• D. 15

Answer 1

The correct option is A 25

push 5
push 2
push 5*2 = 10 (pop 5 and 2)
push 3
push 3
push 2
push 3 + 2 = 5 (pop 2 and 3)
push 5 * 3 =15 (pop 5 and 3)
push 15 + 10 = 25 (pop 15 and 10)