AoC 2017 Day 13: Firewall Puncher

2017-12-13

Source: Packet Scanners

Part 1: Multiple layers are defined with rules of the form:

{index}: {depth}

Each layer will start at position 0, then once per tick will advance towards depth. Once it hits depth-1, it will return to position 0, taking 2*depth-1 per full cycle.

Calculate the sum of index * depth for any scanners that are at position 0 when you pass through them given an initial starting time.

Dynamic Automatic Proxies

2017-12-13

On of the advantages of working in computer programming is that I can work from anywhere I have a computer and an internet connection. One of the disadvantages is that many of the resources that I need to do my job are locked to only be accessible within a specific network (albeit with a bastion host).

I long ago set up my SSH config to create an SSH tunnel and I can proxy many applications through that just by setting the HTTP_PROXY and/or HTTPS_PROXY environment variables. The downside of this though is that if I’m actually on a ‘safe’ network, there’s no reason to use the bastion host and I would actually be putting extra load on it.

My goal: write something that would let me automatically proxy applications when I need to but not when I don’t.

AoC 2017 Day 12: Gridlock

2017-12-12

Source: Digital Plumber

Part 1: A network of nodes is defined by a list of lines formatted as such:

2 <-> 0, 3, 4

AoC 2017 Day 11: It's Full Of Hexagons

2017-12-11

Source: Hex Ed¹

Part 1: Work on a hex grid:

\ n / nw +–+ ne /
-+ +- \ / sw +–+ se / s \

Deterministic Shuffling Using Hashes

2017-12-11

Whenever I create my yearly reading list, I need a way to order the books. Sure, I could just shuffle them normally, but that leads me to the temptation of cheating and re-shuffling them so that the books I want to read most are first. What I really need is a shuffle that will shuffle the same way every time.

Enter: hashsort

AoC 2017 Day 10: Knot Cool

2017-12-10

Source: Knot Hash

Part 1: Starting with a list of the numbers from 1 to n and a list of lengths (as input):

Initialize current_position and skip_size to 0
For each length element in the lengths list:
Reverse the first length elements of the list (starting at current_position)
Move forward by length plus skip_size
Increment skip_size by 1

After applying the above algorithm, what is the product of the first two elements in the list (from the original first position, not the current_position)?

Migrating to Hugo

2017-12-10

A long time ago¹, in a galaxy far, far away², I moved my blog from WordPress to a custom written static blog generator in Racket. And for a while, all was well.

AoC 2017 Day 9: Garbage Gobbler

2017-12-09

Source: Stream Processing

Part 1: An input stream can contain:

groups are delimited by { and }, groups are nestable and may contain garbage or data (objects within a group are comma delimited)
garbage is delimited by < and >, groups cannot be nested within garbage, a ! within garbage is an escape character: !> does not end a garbage segment