Skip to content

Instantly share code, notes, and snippets.

@apropos-cast

apropos-cast/00 Show Notes.md

Last active December 19, 2019 19:17
Show Gist options
  • Star 0 You must be signed in to star a gist
  • Fork 0 You must be signed in to fork a gist
  • Save apropos-cast/69ef76f3ec02642ddebe94827d5bb83d to your computer and use it in GitHub Desktop.
Save apropos-cast/69ef76f3ec02642ddebe94827d5bb83d to your computer and use it in GitHub Desktop.
Download ZIP
December 19, 2019 - Apropos Clojure Show Notes
Raw
00 Show Notes.md

Show date: December 19, 2019

Topics

REPL Exercise

Password rules

From https://adventofcode.com/

Day 4: Secure Container

You arrive at the Venus fuel depot only to discover it's protected by a password. The Elves had written the password on a sticky note, but someone threw it out. However, they do remember a few key facts about the password:

  • It is a six-digit number.
  • The value is within the range given in your puzzle input.
  • Two adjacent digits are the same (like 22 in 122345).
  • Going from left to right, the digits never decrease; they only ever increase or stay the same (like 111123 or 135679).

Other than the range rule, the following are true:

  • 111111 meets these criteria (double 11, never decreases).
  • 223450 does not meet these criteria (decreasing pair of digits 50).
  • 123789 does not meet these criteria (no double).

How many different passwords within the range given in your puzzle input meet these criteria?

Your puzzle input is 168630-718098.

Part Two

An Elf just remembered one more important detail: the two adjacent matching digits are not part of a larger group of matching digits.

Given this additional criterion, but still ignoring the range rule, the following are now true:

  • 112233 meets these criteria because the digits never decrease and all repeated digits are exactly two digits long.
  • 123444 no longer meets the criteria (the repeated 44 is part of a larger group of 444).
  • 111122 meets the criteria (even though 1 is repeated more than twice, it still contains a double 22).

How many different passwords within the range given in your puzzle input meet all of the criteria?

Your puzzle input is 168630-718098.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment