Module day_5

This is my solution for Advent of Code - Day 5: Print Queue

parse_input splits the input into the two sections, delegating these to parse_rules and parse_updates respectively.

Part 1 is solved by sum_valid_middle_pages, with the validation being done by validate_update, and get_middle split out for ease of reuse.

Part 2 is solved by sort_and_sum_invalid_middle_pages, with sort_pages doing the extra work, everything else is reused from part 1.

Functions

• get_middle 🔒
  Utility to get the middle page of an update.
• parse_input 🔒
  Split the list into two sections and parse each
• parse_rules 🔒
  Build the Rules lookup by adding each rule in turn.
• parse_updates 🔒
  Parse the lines of input into lists of page numbers
• run
  The entry point for running the solutions with the ‘real’ puzzle input.
• sort_and_sum_invalid_middle_pages 🔒
  Solution to part 2 - similar to sum_valid_middle_pages, but finds invalid pages and sorts them before extracting thr middle and summing.
• sort_pages 🔒
  Assuming all pairs of pages have rules that specify an ordering for that pair, use that to provide a sorting function for [Itertools::sorted_by].
• sum_valid_middle_pages 🔒
  Solution to part 1, find the valid update lists and sum their middle page.
• validate_update 🔒
  For a given Update, check for each page that a page already in the update list does not need to come after the current page.

Type Aliases

• Rules 🔒
  Rules represented as a lookup from page number to the set of pages that must come after
• Update 🔒
  Updates as a list of page numbers