[Guide] Data Structures: Create a Circular Queue (#34255)

* feat: added circular queue

* fixed code block, adjusted pointer position relative to array entries

* fix: code block

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

@@ -3,8 +3,79 @@ title: Create a Circular Queue
 ---
 ## Create a Circular Queue
 
-This is a stub. <a href='https://github.com/freecodecamp/guides/tree/master/src/pages/certifications/coding-interview-prep/data-structures/create-a-circular-queue/index.md' target='_blank' rel='nofollow'>Help our community expand it</a>.
+### Method:
+- In this challenge we create a Circular Queue data structure.
+- First, we need to create an array of `size` with all elements set to `null`.
+- Then we create an equeue method, which moves the write pointer but doesnt exceed the read pointer.
+- The dequeue method on the other hand, moves the read pointer but doesnt exceed the write pointer.
+- Example:
+  - First, we create an array of length 5:
+  ```output
+  [null, null, null, null, null]
+   ^Read @ 0
+   ^Write @ 0
+  ```
+  - Then we enqueue `a`, `b`, and `c`:
+  ```output
+  [a, b, c, null, null]
+   ^Read @ 0
+            ^Write @ 3
+  ```
+  - Now we dequeue all the enqueued items:
+  ```output
+  [null, null, null, null, null]
+                     ^Read @ 3
+                     ^Write @ 3
+  ```
+  - Finally, we enqueue `d`, `e` and `f`:
+  ```output
+  [f, null, null, d, e]
+                  ^Read @ 3
+      ^Write @ 1
+  ```
+### Solution:
+```js
+class CircularQueue {
+    constructor(size) {
  
-<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>.
+      this.queue = [];
+      this.read = 0;
+      this.write = 0;
+      this.max = size - 1;
  
-<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds  -->
+      while (size > 0) {
+         this.queue.push(null);
+         size--;
+      }
+ 
+    }
+ 
+    print() {
+      return this.queue;
+    }
+ 
+ 
+    enqueue(item) {
+     if (this.queue[this.write] === null){
+       this.queue[this.write++] = item;
+ 
+       if (this.write > this.max) this.write = 0;
+       return item;
+     }
+     return null;
+    }
+ 
+    dequeue() {
+      if (this.queue[this.read] != null){
+        let item = this.queue[this.read];
+        this.queue[this.read++] = null;
+        if (this.read > this.max) this.read = 0;
+        return item;
+      }
+      return null;
+    }
+ }
+ ```
+### References:
+
+- [Wikipedia](https://en.wikipedia.org/wiki/Circular_buffer)