added Big O computation comparison graph

Author: ygit

Big-O Notation.markdown

@@ -18,6 +18,11 @@ Big-O | Name | Description
 **O(n!)** | factorial | **Intolerably slow.** It literally takes a million years to do anything.  
 
 
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+![Comparison of Big O computations](https://upload.wikimedia.org/wikipedia/commons/7/7e/Comparison_computational_complexity.svg)
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 Below are some examples for each category of performance:
 
 **O(1)**