[Guide] Data Structures: Create a Set Class (#34434)

* feat: added solution

* fix: solution

* fix: changed expression to be be more readable

* fix: formatting

curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md

@@ -70,7 +70,18 @@ function Set() {
 
 
 ```js
-function Set() {var collection = []; this.has = function(e){return(collection.indexOf(e) !== -1);};this.values = function() {return collection;};this.add = function(element) {if (!this.has(element)) {collection.push(element);return true;} else {return false;}};}
+function Set() {
+    var collection = [];
+    this.has = function(element) {
+        return (collection.indexOf(element) !== -1);
+    };
+    this.values = function() {
+        return collection;
+    };
+    this.add = function(el) {
+        return this.has(el) ? false : Boolean(collection.push(el));
+    }
+}
 ```
 
 </section>

guide/english/certifications/coding-interview-prep/data-structures/create-a-set-class/index.md

@@ -3,8 +3,30 @@ title: Create a Set Class
 ---
 ## Create a Set Class
 
-This is a stub. <a href='https://github.com/freecodecamp/guides/tree/master/src/pages/certifications/coding-interview-prep/data-structures/create-a-set-class/index.md' target='_blank' rel='nofollow'>Help our community expand it</a>.
+### Method:
+- A Set is an abstract data structure.
+- It can store unique value and the collection is unordered.
+- In this challenge, we have to implement `.add()` method. This method should only add unique values to `collection`.
+  - The method should return `true`, if the value is sucessfully added to the collection, otherwise it should return `false`.
 
-<a href='https://github.com/freecodecamp/guides/blob/master/README.md' target='_blank' rel='nofollow'>This quick style guide will help ensure your pull request gets accepted</a>.
+### Solution:
+```js
+function Set() {
+    // the var collection will hold our set
+    var collection = [];
+    // this method will check for the presence of an element and return true or false
+    this.has = function(element) {
+        return (collection.indexOf(element) !== -1);
+    };
+    // this method will return all the values in the set
+    this.values = function() {
+        return collection;
+    };
+    this.add = function(el) {
+        return this.has(el) ? false : Boolean(collection.push(el));
+    }
+}
+```
 
-<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds  -->
+### Resources:
+- [Wikipedia](https://en.wikipedia.org/wiki/Set_(abstract_data_type))