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Enhance docs, add tests in CircleLinkedList
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@ -1,8 +1,23 @@
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package com.thealgorithms.datastructures.lists;
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/**
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* This class is a circular singly linked list implementation. In a circular linked list,
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* the last node points back to the first node, creating a circular chain.
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*
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* <p>This implementation includes basic operations such as appending elements
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* to the end, removing elements from a specified position, and converting
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* the list to a string representation.
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*
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* @param <E> the type of elements held in this list
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*/
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public class CircleLinkedList<E> {
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private static final class Node<E> {
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/**
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* A static nested class representing a node in the circular linked list.
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*
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* @param <E> the type of element stored in the node
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*/
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static final class Node<E> {
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Node<E> next;
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E value;
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@ -13,44 +28,56 @@ public class CircleLinkedList<E> {
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}
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}
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// For better O.O design this should be private allows for better black box design
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private int size;
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// this will point to dummy node;
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private Node<E> head = null;
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private Node<E> tail = null; // keeping a tail pointer to keep track of the end of list
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Node<E> head = null;
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private Node<E> tail;
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// constructor for class.. here we will make a dummy node for circly linked list implementation
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// with reduced error catching as our list will never be empty;
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/**
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* Initializes a new circular linked list. A dummy head node is used for simplicity,
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* pointing initially to itself to ensure the list is never empty.
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*/
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public CircleLinkedList() {
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// creation of the dummy node
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head = new Node<E>(null, head);
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head = new Node<>(null, head);
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tail = head;
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size = 0;
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}
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// getter for the size... needed because size is private.
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/**
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* Returns the current size of the list.
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*
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* @return the number of elements in the list
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*/
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public int getSize() {
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return size;
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}
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// for the sake of simplistiy this class will only contain the append function or addLast other
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// add functions can be implemented however this is the basses of them all really.
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/**
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* Appends a new element to the end of the list. Throws a NullPointerException if
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* a null value is provided.
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*
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* @param value the value to append to the list
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* @throws NullPointerException if the value is null
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*/
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public void append(E value) {
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if (value == null) {
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// we do not want to add null elements to the list.
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throw new NullPointerException("Cannot add null element to the list");
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}
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// head.next points to the last element;
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if (tail == null) {
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tail = new Node<E>(value, head);
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tail = new Node<>(value, head);
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head.next = tail;
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} else {
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tail.next = new Node<E>(value, head);
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tail.next = new Node<>(value, head);
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tail = tail.next;
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}
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size++;
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}
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/**
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* Returns a string representation of the list in the format "[ element1, element2, ... ]".
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* An empty list is represented as "[]".
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*
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* @return the string representation of the list
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*/
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public String toString() {
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if (size == 0) {
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return "[]";
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@ -68,23 +95,27 @@ public class CircleLinkedList<E> {
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return sb.toString();
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}
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/**
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* Removes and returns the element at the specified position in the list.
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* Throws an IndexOutOfBoundsException if the position is invalid.
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*
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* @param pos the position of the element to remove
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* @return the value of the removed element
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* @throws IndexOutOfBoundsException if the position is out of range
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*/
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public E remove(int pos) {
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if (pos >= size || pos < 0) {
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// catching errors
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throw new IndexOutOfBoundsException("position cannot be greater than size or negative");
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throw new IndexOutOfBoundsException("Position out of bounds");
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}
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// we need to keep track of the element before the element we want to remove we can see why
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// bellow.
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Node<E> before = head;
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for (int i = 1; i <= pos; i++) {
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before = before.next;
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}
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Node<E> destroy = before.next;
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E saved = destroy.value;
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// assigning the next reference to the element following the element we want to remove...
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// the last element will be assigned to the head.
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before.next = before.next.next;
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// scrubbing
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before.next = destroy.next;
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if (destroy == tail) {
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tail = before;
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}
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