Question

USE JAVA

Using recursion, find the largest element in an array. Skeleton code is provided. Please do not change the DataSetDemo code.

Hint: Find the largest element in the subset containing all but the last element. Then compare that maximum to the value of the last element.

Skeleton Code:

DataSet:

/**
Computes the maximum of a set of data values.
*/
public class DataSet
{
private int[] values;
private int first;
private int last;

/**
Constructs a DataSet object.
@param values the data values
@param first the first value in the data set
@param last the last value in the data set
*/
public DataSet(int[] values, int first, int last)
{
this.values = values;
this.first = first;
this.last = last;
}

/**
Gets the maximum in the set of data values
@return the maximum value in the set
*/
public int getMaximum()
{
. . . // add your code here.
}
}
DataSetDemo Code: (DO NOT CHANGE THIS)

import java.util.Random;

/**
A tester class for the recursive maximum. DO NOT CHANGE THIS CODE.
*/
public class DataSetDemo
{
public static void main(String[] args)
{
int[] values = { 1, 10, 100, -1, -10, -100, 100, 0 };
DataSet d = new DataSet(values, 0, values.length - 1);
System.out.println("Maximum: " + d.getMaximum());
System.out.println("Expected: 100");
}
}

Answer 1

/**
 * Computes the maximum of a set of data values.
 */
public class DataSet {
    private int[] values;
    private int first;
    private int last;

    /**
     * Constructs a DataSet object.
     *
     * @param values the data values
     * @param first  the first value in the data set
     * @param last   the last value in the data set
     */
    public DataSet(int[] values, int first, int last) {
        this.values = values;
        this.first = first;
        this.last = last;
    }

    /**
     * Gets the maximum in the set of data values
     *
     * @return the maximum value in the set
     */
    public int getMaximum() {
        return getMaximum(first, last);
    }

    private int getMaximum(int start, int end) {
        if (start == end) {
            return values[start];
        } else {
            int max = getMaximum(start, end - 1);
            if (values[end] > max)
                max = values[end];
            return max;
        }
    }
}