Update README.md

Author: tobbie

README.md

@@ -33,3 +33,9 @@ To get started, clone the repo, build the project, then run `dotnet test` to see
 
 This solution requires `.NET 6` to run. Happy coding! :)
 
+<img width="672" alt="big-o-cheetsheet" src="https://github.com/tobbie/c-sharp-algorithms/assets/4679573/be30f7a7-94df-4fb0-96e5-be215e87a743">
+[source(https://www.bigocheatsheet.com/)]
+
+### To contribute
+Please visit [this page(https://github.com/tobbie/c-sharp-algorithms/blob/main/CONTRIBUTING.md)]
+