https://adventofcode.com/2018/day/1
Day 1 was relatively straightforward. I had never programmed with Elixir before, and I had been interested in the language after watching its mini-documentary on youtube ( https://www.youtube.com/watch?v=lxYFOM3UJzo ), so I gave it a shot and wrote my first elixir programs ever.
Languages Solved In: Elixir
Problem: Sum all numbers in a file.
Approach: Solved easily by reading in the file and piping to Enum.sum.
Problem: Keep a running sum of all numbers in a file, until a sum is repeated - that's the answer. If no answer is found after summing all the numbers, read the file repeatedly until an answer is found.
Approach: I used Enum.reduce to build my own summing function. But my accumulator did not only hold the sum; it also contained a seen_map, where I track every sum that's been seen.
As duplicates are found, I push them onto the seen_multiple array. After each scan of the file, I check seen_multiple to see if we've found an answer and either return it or start another scan. Because it's an array, I know which answer was found first.
Downsides: Answer checks are only done after each file is scanned completely, so the program might do extraneous work, especially with large files. At the time, I didn't know how to make the Enum.reduce stop calculating early. However, if I were to rewrite this, I might use pattern matching to make the accumulator contain a signal that it's done and to stop computing.