Add big-o-notation guide

content/guides.json

@@ -1,4 +1,14 @@
 [
+  {
+    "title": "Big-O Notation",
+    "description": "Easy to understand explanation of Big-O notation without any fancy terms",
+    "url": "/guides/big-o-notation",
+    "fileName": "big-o-notation",
+    "featured": true,
+    "author": "kamranahmedse",
+    "updatedAt": "2020-03-14T15:48:21.191Z",
+    "createdAt": "2020-03-14T15:48:21.191Z"
+  },
   {
     "title": "How does the internet work?",
     "description": "Learn the basics of internet and everything involved with this short video series",

content/guides/big-o-notation.md

@@ -0,0 +1,5 @@
+Big-O notation is the mathematical notation that helps analyse the algorithms to get an idea about how they might perform as the input grows. The image below explains Big-O in a simple way without using any fancy terminology. 
+
+![](/guides/big-o-notation.png)
+
+Here is the [original tweet](https://twitter.com/kamranahmedse/status/1235708842610212864) where this image was posted.

public/sitemap.xml

@@ -30,6 +30,12 @@
               <lastmod>2020-01-29T07:49:29.706Z</lastmod>
               <priority>1.0</priority>
           </url>
+<url>
+              <loc>https://roadmap.sh/guides/big-o-notation</loc>
+              <changefreq>monthly</changefreq>
+              <lastmod>2020-03-14T15:48:21.191Z</lastmod>
+              <priority>1.0</priority>
+          </url>
 <url>
               <loc>https://roadmap.sh/guides/what-is-internet</loc>
               <changefreq>monthly</changefreq>