294 lines
5.9 KiB
Markdown
294 lines
5.9 KiB
Markdown
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---
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id: 587d8251367417b2b2512c64
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title: Search within a Linked List
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challengeType: 1
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forumTopicId: 301715
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dashedName: search-within-a-linked-list
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---
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# --description--
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Let's add a few more useful methods to our linked list class. Wouldn't it be useful if we could tell if our list was empty or not, as with our `Stack` and `Queue` classes?
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We should also be able to find specific elements in our linked list. Traversing through data structures is something you'll want to get a lot of practice with! Let's create an `indexOf` method that takes an `element` as an argument, and returns that element's `index` in the linked list. If the element is not found in the linked list, return `-1`.
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Let's also implement a method that does the opposite: an `elementAt` method that takes an `index` as an argument and returns the `element` at the given `index`. If no `element` is found, return `undefined`.
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# --instructions--
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Write an `isEmpty` method that checks if the linked list is empty, an `indexOf` method that returns the `index` of a given element, and an `elementAt` that returns an `element` at a given `index.`
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# --hints--
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Your `LinkedList` class should have an `isEmpty` method.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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return typeof test.isEmpty === 'function';
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})()
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);
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```
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Your `isEmpty` method should return `false` when there is at least one element in linked list.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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test.add('cat');
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test.add('dog');
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test.add('kitten');
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return test.isEmpty() === false;
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})()
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);
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```
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Your `isEmpty` method should return `true` when there are no elements in linked list.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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return test.isEmpty() === true;
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})()
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);
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```
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Your `LinkedList` class should have an `indexOf` method.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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return typeof test.indexOf === 'function';
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})()
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);
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```
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Your `indexOf` method should return the index of a given element found in linked list.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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test.add('cat');
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test.add('dog');
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test.add('kitten');
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return test.indexOf('cat') === 0;
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})()
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);
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```
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Your `indexOf` method should return `-1` if the given element is not found in linked list
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```js
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assert(
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(function () {
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var test = new LinkedList();
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test.add('cat');
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test.add('dog');
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test.add('kitten');
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return test.indexOf('pony') === -1;
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})()
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);
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```
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Your `LinkedList` class should have an `elementAt` method.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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return typeof test.elementAt === 'function';
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})()
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);
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```
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Your `elementAt` method should return the element found at a given index in linked list.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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test.add('cat');
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test.add('dog');
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test.add('kitten');
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return test.elementAt(1) === 'dog';
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})()
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);
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```
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Your `elementAt` method should return `undefined` if the given element is not found at a given index in linked list.
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```js
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assert(
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(function () {
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var test = new LinkedList();
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test.add('cat');
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test.add('dog');
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test.add('kitten');
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return test.elementAt(5) === undefined;
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})()
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);
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```
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# --seed--
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## --seed-contents--
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```js
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function LinkedList() {
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var length = 0;
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var head = null;
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var Node = function(element){
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this.element = element;
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this.next = null;
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};
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this.size = function() {
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return length;
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};
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this.head = function(){
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return head;
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};
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this.add = function(element){
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var node = new Node(element);
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if(head === null){
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head = node;
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} else {
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var currentNode = head;
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while(currentNode.next){
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currentNode = currentNode.next;
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}
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currentNode.next = node;
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}
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length++;
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};
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this.remove = function(element){
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var currentNode = head;
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var previousNode;
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if(currentNode.element === element){
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head = currentNode.next;
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} else {
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while(currentNode.element !== element) {
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previousNode = currentNode;
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currentNode = currentNode.next;
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}
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previousNode.next = currentNode.next;
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}
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length --;
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};
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// Only change code below this line
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// Only change code above this line
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}
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```
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# --solutions--
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```js
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function LinkedList() {
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var length = 0;
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var head = null;
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var Node = function(element){
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this.element = element;
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this.next = null;
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};
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this.size = function() {
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return length;
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};
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this.head = function(){
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return head;
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};
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this.add = function(element){
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var node = new Node(element);
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if(head === null){
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head = node;
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} else {
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var currentNode = head;
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while(currentNode.next){
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currentNode = currentNode.next;
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}
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currentNode.next = node;
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}
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length++;
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};
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this.remove = function(element){
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var currentNode = head;
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var previousNode;
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if(currentNode.element === element){
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head = currentNode.next;
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} else {
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while(currentNode.element !== element) {
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previousNode = currentNode;
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currentNode = currentNode.next;
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}
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previousNode.next = currentNode.next;
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}
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length --;
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};
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this.indexOf = function(element) {
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if (head === null) return -1
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let current = head;
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let index = 0;
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while (current.element !== element && current.next !== null) {
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current = current.next;
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index++
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}
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if (current.element !== element && current.next === null) {
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return -1
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}
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return index;
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}
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this.elementAt = function(index) {
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if (head === null) return undefined;
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let current = head;
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let currentIndex = 0;
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while (currentIndex !== index && current.next !== null) {
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current = current.next;
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currentIndex++
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}
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if (currentIndex !== index && current.next === null) {
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return undefined;
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}
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return current.element;
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}
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this.isEmpty = function() {
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return length === 0;
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}
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}
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```
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