Update index.md (#19328)

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

@@ -3,8 +3,78 @@ title: Create a Queue Class
 ---
 ## Create a Queue Class
 
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+### Method:
+- A Queue is an abstract Data Structure.
+- A Queue folow FIFO/LILO principle.
+- In this challenge we nede to implement `enqueue()`, `dequeue()`, `front()`, `size()`, `isEmpty()` methods.
+  - `enqueue()` - This method adds the element to the queue.
+  - `dequeue()` - This method removes the first element from the queue.
+  - `front()` - This method returns the first element in the queue that'd be dequeue'd.
+  - `size()` - This method returns the size of the queue.
+  - `isEmpty()` - This method returns if the queue is empty.
+- 
+  | DS    | Access | Search | Insert | Delete |
+  | ----- | ------ | ------ | ------ | ------ |
+  | Queue |   n    |    n   |   1    |    1   |
   
-<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds  -->
+ - ![Queue in action](https://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Data_Queue.svg/405px-Data_Queue.svg.png)
+
+### Solution:
+
+#### Basic:
+##### Note: 
+- This solution is not exactly a queue, the shift() method used in the dequeue() method is of complexity `O(n)` and not `O(1)`. However, the advanced solution rectifies this and uses Object(HashTables) instead of Array to implement Queue. 
+```js
+function Queue () { 
+    var collection = [];
+    this.print = function() {
+        console.log(collection);
+    };
+    this.enqueue = function(val){
+        collection.push(val);
+    };
+    this.dequeue = function(){
+        return collection.shift();
+    }
+    this.front = function(){
+        return collection[0];
+    }
+    this.size = function(){
+        return collection.length;
+    }
+    this.isEmpty = function(){
+        return collection.length === 0;
+    }
+}
+```
+#### Advanced - ES6 class syntax:
+```js
+class Queue {
+    constructor(){
+        this.collection = {};
+        this.start = 0;
+        this.end = 0;
+    }
+    print(){
+        console.log(this.collection);
+    }
+    enqueue(val){
+        this.collection[this.end++] = val; 
+    }
+    dequeue(){
+        return this.collection[this.start++];
+    }
+    front(){
+        return this.collection[this.start];
+    }
+    size(){
+        return this.end - this.start;
+    }
+    isEmpty(){
+        return this.size() === 0;
+    }
+}
+```
+### References:
+- [Wikipedia](https://en.wikipedia.org/wiki/Queue_(abstract_data_type))