Documentation | Started 'Most Challenging Day' (Part of #7)

README.md

@@ -4,12 +4,24 @@
 ![GitHub closed issues](https://img.shields.io/github/issues-closed/TomPlum/advent-of-code-2019?color=brightgreen)
 ![GitHub](https://img.shields.io/github/license/TomPlum/advent-of-code-2019?color=informational)
 
+## About
 Working through it while learning [Kotlin](https://kotlinlang.org/). Acts as a nice format for personal development. 
 I'm treating the code-base a little more _enterprise-esque_, for lack of a better term.
-Meaning I'm focusing more on design, readability, ensuring code is test-driven with full coverage etc. 
+Meaning I'm focusing more on design, readability, and ensuring code is test-driven with full coverage etc. 
 This doesn't mean, however, that I'm not considering performance. Any solutions that don't meet a respectable order of
 runtime complexity will be refactored and improved upon in a later pass of the days.
 
+## The Days
+
+### Most Challenging
+Day 18. This day was add one. Usually, the implementation is the 'easy' bit, and figuring out the theory behind the
+solution is the harder bit that can take a while. However, Day 18s theory was simple. It was a maze
+filled with doors with corresponding keys, and you had the find the shortest path to collect all keys. So it was just
+a case of using an exhaustive DFS (Depth First Search) Algorithm that would graph all the keys and their respective 
+weights to any other accessible ones. Then running Djiksta's Algorithm on the weighted graph to find the shortest path.
+I just couldn't figure out how to implement it. I spent so many hours trying different things until I eventually
+managed to get 4 of the 5 examples working. Example 5, however, just ran indefinitely and so did my puzzle input.
+
 ## Answer Table
 
 | Day 	| Part 1 	| Part 2 	        | Name                                      |