Question

With reference to the code given below, answer the questions that follow along with dry run/working.boolean num(int x)

{ int a=1}
   for (int c=x; c>0; c/<10}
      a*=10;
   return (x*x%a)=x;
}

1. What will the function num() return when the value of x = 25?
2. What is the method num() performing?

Answer 1

1. True
2. The function num( ) is checking whether the argument received is an automorphic number or not.

Explanation:

The function num() gets a number as the input x. Using the while loop, it then determines the amount of digits, say 'n' in the number. It then gets the last n digits of the square of x. If they match, it returns true.

(This is a test for an automorphic number. An automorphic number is one that is found at the end of its square. Example: 25)