Elixir

This one took way to long to do because I got hung up on what turned out to just be forgetting to rename functions when copying code from part 1 to part 2.

I did part 1 in language but turned to regex for part 2.

#!/usr/bin/elixir

defmodule GiftShopDatabase do

def getRanges(filename) do
	{:ok, content} = File.read(filename)
	input = String.trim(content)
	ranges = []
	currLowerLim = ""
	currNum = ""
	parseRanges(input, ranges, currLowerLim, currNum)
end

defguardp isDigit(c) when c in ?0..?9

defp parseRanges(input, ranges, currLowerLim, currNum) do
	case input do
		<<>> -> Enum.reverse([{currLowerLim,IO.iodata_to_binary(currNum)} | ranges])
		<<",", rest::binary>> ->
			#newUpperLim = IO.iodata_to_binary(currNum) |> String.to_integer
			newUpperLim = IO.iodata_to_binary(currNum)
			parseRanges(rest, [{currLowerLim,newUpperLim} | ranges], currLowerLim, "")
		<<"-", rest::binary>> ->
			#newLowerLim = IO.iodata_to_binary(currNum) |> String.to_integer
			newLowerLim = IO.iodata_to_binary(currNum)
			parseRanges(rest, ranges, newLowerLim, "")
		<<char::utf8, rest::binary>> when isDigit(char) ->
			parseRanges(rest, ranges, currLowerLim, [currNum | <<char>>])
		other -> raise "[ ERROR ] unkown input:#{inspect(other)}"
	end
end

def getInvIDSum(ranges, invIDSum) do
	case ranges do
		[] -> invIDSumString.to_integer(elem(range,0)), invIDSum))
		[range | rest] -> getInvIDSum(rest, invIDSum+checkRange(range, String.to_integer(elem(range,0)), 0))
		other -> raise "[ ERROR ] invalid ranges given:#{inspect(other)}"
	end
end

defp checkRange(range, currID, invIDSum) do
	strUpperLim = String.to_integer(elem(range,1))
	unevenDigitCount = rem(String.length(Integer.to_string(currID)),2)
	case currID do
		_ when currID > strUpperLim -> invIDSum
		_ when unevenDigitCount == 1 -> checkRange(range, currID+1, invIDSum)
		_ -> checkRange(range, currID+1, invIDSum + checkID(currID))
	end
end

defp checkID(currID) do
	pow = :math.pow(10,String.length(Integer.to_string(currID))/2)
	front = floor(currID/pow)
	back = currID - floor(front*pow)
	if front == back, do: currID, else: 0
end

def getInvIDSumPart2(ranges, invIDSum) do
	case ranges do
		[] -> invIDSum
		#[range | rest] -> getInvIDSumPart2(rest, invIDSum+checkRangePart2(range, elem(range,0), invIDSum))
		[range | rest] -> getInvIDSumPart2(rest, invIDSum+checkRangePart2(range, elem(range,0), 0))
		other -> raise "[ ERROR ] invalid ranges given:#{inspect(other)}"
	end
end

def checkRangePart2(range, currID, invIDSum) do
	numID = String.to_integer(currID)
	numUpperLim = String.to_integer(elem(range,1))
	case currID do
		_ when numID > numUpperLim -> invIDSum
		_ when numID < 10 -> checkRangePart2(range, Integer.to_string(String.to_integer(currID)+1), invIDSum)
		_ -> checkRangePart2(range, Integer.to_string(String.to_integer(currID)+1), invIDSum + checkIDPart2(currID,1,floor(String.length(currID)/2)))
	end
end

def checkIDPart2(currID, currLen, maxLen) do
	regex = "(#{String.slice(currID,0,currLen)})+"
	regexComp = Regex.compile(regex)
	res = Regex.run(elem(regexComp,1), currID)
	case res do
		[_, _] when currLen > maxLen or maxLen == 0 -> 0
		[longestMatch, _] when longestMatch == currID -> String.to_integer(currID)
		[_, _] -> checkIDPart2(currID, currLen+1, maxLen)
		_ -> 0
	end
end

end #module


IO.puts "### Part 1 ###"
ranges = GiftShopDatabase.getRanges("input/day02Input.txt")
IO.puts "[ INFO ] ranges:#{inspect(ranges)}"
invIDSum = GiftShopDatabase.getInvIDSum(ranges, 0)
IO.puts "[ INFO ] invalid ID sum:#{invIDSum}"

IO.puts "### Part 2 ###"
ranges = GiftShopDatabase.getRanges("input/day02Input.txt")
IO.puts "[ INFO ] ranges:#{inspect(ranges)}"
invIDSum = GiftShopDatabase.getInvIDSumPart2(ranges, 0)
IO.puts "[ INFO ] invalid ID sum:#{invIDSum}"