My take-away from day 5’s code is to keep things simple. And read all of the documentation because I’ve been creating functions when I don’t need to.
My first attempt at the challenge was to do a single pass through the characters in pairs, remove them if the fitted the matching criteria which created a new string to parse and the changing the current ‘cursor’ position to handle the string length change so that I didn’t skip letters. It worked but it was as messy as it sounds (possibly more-so!) and it was really slow.
Solving part 2 whilst part one is slow is possible but I’d have probably had time for a nap whilst it ran so I decided to try a simpler approach. This time I converted the polymers into a character list (I originally used graphemes but saw one of a few great tricks in @sionide21’s solution… see below) so that I could use recursive pattern matched functions to process the polymers. If at the end of a run through the characters the resulting string was shorter than the original I’d re-process the characters and carry on until changes had been exhausted. This was much, much faster.
Part 2 was where I encountered some new standard library functions and in particular Enum.uniq/1 and Enum.reject/2, both of which allowed me to remove Enum.reduce/3 calls. The combination of Map.values/1 and Enum.min/1 were also really helpful at the end of the pipeline and saved me from writing yet another Enum.reduce/3.
After writing my code I looked at @sionide21’s solution which helped me tidy a few things up. He’d used recursive pattern matching functions too but passed a boolean flag between them to indicate whether the polymers had been edited. This is cleaner. He also took advantage of character codes to handle upper and lower case checks: abs(a - b) == 32. I’d used an if statement inside a single function but I thought of @pragdave and changed it and could then use two functions. If I’d retro-fitted the change flag in place of my string length parameter I could have done the same for the last function.
Overall I was really pleased with how today’s solution turned out and it was gratifying to see that I was heading in the same direction as more experienced Elixir developers.
