Consider the following C program: #include #define EOF -1 void push(int); /* push the argument on the stack...

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 flagError();

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 == '+') ? m + n : m * n;
            push(r);
        } else if (c != ' ')
            flagError();
    }
    printf("%d
", pop());
}

What is the output of the above program for the following input?
2 + 3 . 3 . 2 + *

Wait — the input shown in the image is: 2 + 3 . 3 . 2 + *

What is the output of the above program for the input: 5 2 + 3 . 3 . 2 + *

A. 15
B. 25
C. 30
D. 150

Accepted Answer

A. 15 — the program evaluates the stack-based postfix expression and outputs 15. The program reads characters one by one. If a character is a digit, it pushes it onto the stack. If it's '+' or '*', it pops two values, performs the operation, and pushes the result. At the end, it prints the top of the stack. The input encodes an expression using a stack-based evaluation strategy. We need to simulate the program with the given input.