Question

java

- A recursive method findR() to search for a number in list (ArrayList)

- A recursive algorithm to multiply two positive integers m and n using repeated addition.

with output

Answer 1

Thanks for the quesiton, here are the two recursive methods in implemented in Java with sample out.

==================================================================================

import java.util.ArrayList;

public class Recursive {

// method takes in the arraylist, the number to search and the current index = 0

    public static void findR(ArrayList<Integer> numbers, int searchNumber, int startingIndex) {

        if (startingIndex == numbers.size()) {
            System.out.println("Number :" + searchNumber + " does not exist");
            return;
        } else {
            if (numbers.get(startingIndex) == searchNumber) {

                System.out.println("Number :" + searchNumber + " exist in the list");
                return;
           } else {
                findR(numbers, searchNumber, startingIndex + 1);
            }
        }

    }

// method recursively multiplies two number using addition

    public static int multiplyByAddition(int x, int y) {


        if (y == 0) {
            return 0;
        } else {

           return x + multiplyByAddition(x, y - 1);
        }

    }


    public static void main(String[] args) {

        ArrayList<Integer> numbers = new ArrayList<>();
        for (int i = 1; i <= 10; i++) numbers.add(i);

        findR(numbers, 8, 0);
        findR(numbers, 18, 0);

        System.out.println("multiplyByAddition(6,7) = " + multiplyByAddition(6, 7));


    }
}

==============================================================================