AoC Day 9 was a lesson in what works fantastic for the first part, fails miserably for the 2nd part. Its one of the frustrations but also challenges of AoC, where you only get half of the final requirements to start. The puzzle input you get is just a string of single digit numbers (i.e. 12345) The digits in the string go back and forth in what they represent. The first digit is the size of a file, followed by the size of free space between that file and the next file. So for my example above, I have a file that is one block big, followed by two free blocks. Followed by a file three blocks big, followed by four free blocks, finally followed by a five block file.

AoC Day 8 has us mapping interactions between items on a grid. The input is a large grid filled with mostly blank (“.”) spaces. However, across the grid are multiple “antennas” identified by the frequency that they are broadcasting (frequency is identified by an arbitrary letter or number). The challenge is to find interactions between the various antennas that are broadcasting on the same frequency.

AoC Day 7 has us trying to figure out a slightly new kind of math. Our input is a multiline list. The list starts with a single integer, followed by a colon (“:”), and then multiple comma separated integers. Our goal is to find the number of lines, where it is possible to reach the answer (the first integer) using only addition or multiplication of the various other numbers. For example, if a line was 190: 10 19, we could reach 190 by multiplying 10 and 19.

For day 6 of AoC, our input is a grid showing the setup of a room. Most of the space is marked with periods (“.”), but there are some that are marked with a pound sign (“#”) to denote some sort of obstruction. Also within the grid, is the starting location of a guard, whose route you have to map out.

Day 5’s input is broken up into two parts. Part 1 lists a series of “rules”. Each rule is a single line and is made up of two integers, separated by a pipe (“|”). The rule indicates that the first integer must be before the second integer in order for the series of pages to be valid.

Advent of Code Day 4 was a bit of a word search on steroids. The puzzle input was a very large grid of X, M, A, and Ss. In part 1 we were looking for all of the “XMAS” matches in the puzzle going vertical, horizontal, and diagonal both forwards and backwards.

Day 3 of AoC this year was the first day that honestly made me work. The first part of it pretty straight forward. You’re given a very long string input (mine was just over 18,000 characters). Within that string is a wide variety of alphabetical, numerical, and special characters. You’re looking for a sequence that is “mul(#,#)” where # is an number 1 – 3 numbers long (i.e. mul(123,1) would be valid). Whenever you find that sequence you want to sum the product of those two numbers in the parenthesis.

Day 2 of AoC starts off with a fairly straightforward problem. Our input is a series of lines, with each line containing an arbitrary number of integers. The example data shows each line having 5 numbers, but the actual input has more or less depending on the exact line you’re on (so it’s not a one size fits all thing). Our task is to count the number of lines that meet three rules.