Update Linked List classes

src/com/codefortomorrow/advanced/chapter16/practice/TestSinglyLinkedList.java

@@ -0,0 +1,43 @@
+package com.codefortomorrow.advanced.chapter16.practice;
+
+/**
+ * @author ArmeetJatyani
+ * March 2021
+ *
+ * Implement a simple LinkedList
+ * You will need to create a LinkedListNode class, which represents each item/node in the linked list
+ * Assume that the elements in the linked list are all of type int
+ * Required functionality...
+ * - head(): get head node of list
+ * - tail(): get tail node of list
+ * - add(): add element to the end of the list
+ * - insert(): insert an element at a given index position
+ * - push(): add element to the beginning of the list
+ * - pop(): remove head of list and return the node that was removed
+ * - clear(): remove all elements in the list
+ * - toString(): return a String representation of the list
+ * 
+ * Create a driver class called TestLinkedList. In the main method, create an instance
+ * of LinkedList and test all of its methods at least once. (Print the list as needed
+ * to prove the methods worked.)
+ */
+
+public class TestSinglyLinkedList {
+
+    public static void main(String[] args) {
+        // write your code here
+
+    }
+}
+
+class Node {
+    // write your code here
+}
+
+class LinkedListNode extends Node {
+    // write your code here
+}
+
+class SinglyLinkedList {
+    // write your code here
+}

src/com/codefortomorrow/advanced/chapter16/solutions/LinkedList.java → src/com/codefortomorrow/advanced/chapter16/solutions/TestSinglyLinkedList.java

@@ -8,30 +8,79 @@
  * You will need to create a LinkedListNode class, which represents each item/node in the linked list
  * Assume that the elements in the linked list are all of type int
  * Required functionality...
- * - head(): get head of list
- * - tail(): get tail of list
- * - add(): add to tail of list
- * - push(): push to head of list
- * - pop(): remove head of list
+ * - head(): get head node of list
+ * - tail(): get tail node of list
+ * - add(): add element to the end of the list
+ * - insert(): insert an element at a given index position
+ * - push(): add element to the beginning of the list
+ * - pop(): remove head of list and return the node that was removed
+ * - clear(): remove all elements in the list
  * - toString(): return a String representation of the list
+ * 
+ * Create a driver class called TestLinkedList. In the main method, create an instance
+ * of LinkedList and test all of its methods at least once. (Print the list as needed
+ * to prove the methods worked.)
  */
 
-public class LinkedList {
+public class TestSinglyLinkedList {
+    public static void main(String[] args) {
+        // test default constructor
+        SinglyLinkedList list = new SinglyLinkedList();
+        System.out.println("Empty linked list: " + list);
+
+        // test 1 arg constructor
+        list = new SinglyLinkedList(10);
+        System.out.println("Linked list with 1 element: " + list);
+
+        // test add method
+        list.add(5);
+        list.add(7);
+        list.add(12);
+        list.add(2);
+        System.out.println("Test add(): " + list);
+
+        // test insert method
+        list.insert(13, 0);
+        System.out.println("Test insert(): " + list);
+        list.insert(1, 6);
+        System.out.println("Test insert(): " + list);
+        list.insert(4, 3);
+        System.out.println("Test insert(): " + list);
+
+        // test head and tail methods
+        System.out.println("Head: " + list.head().value());
+        System.out.println("Tail: " + list.tail().value());
+
+        // test push
+        list.push(21);
+        System.out.println("Test push(): " + list);
+
+        // test pop
+        System.out.println("Popped element: " + list.pop().value());
+        System.out.println("Test pop(): " + list);
+
+        // test clear
+        list.clear();
+        System.out.println("Test clear(): " + list);
+    }
+}
+
+class SinglyLinkedList {
 
     private LinkedListNode head;
 
     /**
      * default constructor
      */
-    public LinkedList() {
+    public SinglyLinkedList() {
         head = null;
     }
 
     /**
      * constructor with first value
      * @param value  first element in the linked list
      */
-    public LinkedList(int value) {
+    public SinglyLinkedList(int value) {
         // create first node
         head = new LinkedListNode(value, null);
     }
@@ -73,15 +122,50 @@ public void add(int value) {
     }
 
     /**
-     * push (add element to head of linkedlist)
+     * Inserts a value at a given position in the linked list
+     * @param value  value to insert
+     * @param index  where to insert the value
+     */
+    public void insert(int value, int index) {
+        // Verify valid index number
+        if (index < 0) System.out.print("Invalid position");
+
+        // Create new node and keep track of current node
+        LinkedListNode new_node = new LinkedListNode(value, null);
+        LinkedListNode current = head;
+
+        // If index is 0, set new node as head
+        if (index == 0) {
+            new_node.setNext(head);
+            head = new_node;
+        } else {
+            while (index-- >= 0) {
+                if (index == 0) {
+                    // Add new node after current position
+                    new_node.setNext(current.next());
+                    current.setNext(new_node);
+                    break;
+                }
+                // Check if index is out of bounds (reaches end)
+                if (current.next() == null) {
+                    System.out.println("Out of bounds");
+                    break;
+                }
+                current = current.next();
+            }
+        }
+    }
+
+    /**
+     * Adds element to head of the linked list
      */
     public void push(int value) {
         LinkedListNode newHead = new LinkedListNode(value, head);
         head = newHead;
     }
 
     /**
-     * pop (remove and return head of linkedlist)
+     * Removes and returns the head of the linked list
      * @return the node that was removed
      */
     public LinkedListNode pop() {
@@ -90,12 +174,23 @@ public LinkedListNode pop() {
         return popped;
     }
 
+    /**
+     * Removes all elements in the list
+     */
+    public void clear() {
+        head = null;
+    }
+
     /**
      * Returns a String version of the LinkedList
      * @return a String version of the LinkedList
      */
     @Override
     public String toString() {
+        if (head == null) {
+            return "[]";
+        }
+
         String list = "[";
         LinkedListNode current = head;
         if (current == null) return null;