Question

Objectives: use Scite

1. Use recursion to solve a problem

2. Create classes to model objects

Problem 1: Compute greatest common divisor using recursion (filename: TestRecusiveGCD.java) The gcd(m, n) can be defined recursively as follows: If m % n is 0, gcd (m, n) is n. Otherwise, gcd(m, n) is gcd(n, m % n). Write a recursive method to find the GCD of two given integers. Write a test program that prompts the user to enter two integers, calls the method above, and displays their GCD.

Problem 2: Print the digits in an integer reversely (filename: TestReverseDigits.java) Write a recursive method that displays an integer value reversely on the console using the following header: public static void reverseDisplay(int value) For example, reverseDisplay(12345) displays 54321. Write a test program that prompts the user to enter an integer, invokes the method above, and displays its reversal.

Answer 1

TestRecusiveGCD.java

class TestRecusiveGCD
{
   public static void main(String[] args)
   {
       System.out.println(gcd(2,5));
       System.out.println(gcd(10,5));
       System.out.println(gcd(24,16));
       System.out.println(gcd(11,12));
   }
   public static int gcd(int m, int n)
   {
       if(m%n==0)
       {
           return n;
       }
       return gcd(m,m%n);
   }
}

output screenshot:

TestReverseDigits.java

class TestReverseDigits
{
   public static void main(String[] args)
   {
       reverseDisplay(12345);
       System.out.println();
       reverseDisplay(10000);
       System.out.println();
       reverseDisplay(1234567890);
       System.out.println();
   }
   public static void reverseDisplay(int n)
   {
       if(n<10)
       {
           System.out.print(n);  
           return;
       }
       System.out.print(n%10);
       reverseDisplay(n/10);
   }
}

output screenshot: