(Java Linked Lists) create method getGroupedString in class ListUtilities. refer to test cases and Node class for more info. pay attenion to noAliasing method in test cases:

public class Node { private E element; private Node next; /* * Constructor */ public Node(E e, Node n) { element = e; next = n; } /* * Accessors */ public E getElement() { return element; } public Node getNext() { return next; } /* * Mutators */ public void setElement(E e) { element = e; } public void setNext(Node n) { next = n; } }

@Test public void test_getGroupedStrings_01() { ListUtilities util = new ListUtilities(); Node input = new Node<>("vwxyzj", new Node<>("xy", new Node<>("ghic", new Node<>("pqrstu", new Node<>("def", new Node<>("bc", new Node<>("a", new Node<>("", null)))))))); /* * Calling getGroupedStrings(input, m, n) returns a chain of nodes * which groups all elements from the input chain as follows, from left to right: * Group 1: strings whose lengths are less than m * Group 2: strings whose lengths are greater than or equal to m and less than n * Group 3: strings whose lengths are greater than or equal to n * * Requirements: * - The input and output chains are equally long. * - Each group in the output chain preserves the order in which its elements appear in the input chain. * * Assumptions: * - Assume that m <= n. * - When m = n, it means that group2 is empty. * (say m = n = 3: there is no string whose length is >= 3 and < 3). */ Node output = util.getGroupedStrings(input, 2, 4); /* * Group 1: strings from the input chain whose lengths are * less than 2 (i.e., 0, 1) */ assertEquals("a" , output.getElement()); assertEquals("" , output.getNext().getElement()); /* * Group 2: strings from the input chain whose lengths are * greater than or equal to 2 and less than 4 (i.e., 2, 3) */ assertEquals("xy" , output.getNext().getNext().getElement()); assertEquals("def" , output.getNext().getNext().getNext().getElement()); assertEquals("bc" , output.getNext().getNext().getNext().getNext().getElement()); /* * Group 3: strings from the input chain whose lengths are * greater than or equal to 4 (i.e., 4, 5, ...) */ assertEquals("vwxyzj" , output.getNext().getNext().getNext().getNext().getNext().getElement()); assertEquals("ghic" , output.getNext().getNext().getNext().getNext().getNext().getNext().getElement()); assertEquals("pqrstu" , output.getNext().getNext().getNext().getNext().getNext().getNext().getNext().getElement()); assertNull(output.getNext().getNext().getNext().getNext().getNext().getNext().getNext().getNext()); /* * The input and output chains do not share any node references in common. * i.e., there is no reference aliasing. */ assertTrue(noAliasing(input, output)); }

private boolean noAliasing(Node n1, Node n2) { Node current1 = n1; Node current2 = n2; boolean found = false; while(current1 != null && !found) { while(current2 != null && !found) { found = current1 == current2; current2 = current2.getNext(); } current1 = current1.getNext(); current2 = n2; } return !found; }