ISRO | ISRO CS 2007 | Question 23

Study the following program:

// precondition: x>=0
public void demo(int x)
{
    System.out.print(x % 10);
    if (x % 10 != 0) {
        demo(x / 10);
    }
    System.out.print(x % 10);
}

Which of the following is printed as a result of the call demo(1234)?

(A)

1441

(B)

3443

(C)

12344321

(D)

4321001234

Answer: (D)
Explanation:

In the above code, the first print statement is executed and prints the value obtained after performing a modulus of 10, and recursively another function is called with the value divided by 10. And after the return of the function, it prints the values again. 

• demo(1234) 
  • prints 4
  • call demo(123)  
    • prints 3
    • call demo(12)  
      • prints 2
      • call demo(1)  
        • prints 1
        • call demo (0) 
          • prints 0
          • prints 0
        • prints 1 
      • prints 2 
    • prints 3 
  • prints 4.

So, option (D) is correct.

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