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 \

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)?

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

The score of a single group is equal to how many times it is nested (the innermost group of {{{}}} has score 3).

The score of a stream is the sum of the scores of all groups in that stream.

What is the total score of your input?

AoC 2017 Day 8: Conditiputer

2017-12-08

Source: I Heard You Like Registers¹

Part 1: Given a set of registers initialized to 0, interpret a series of instruction of the form:

{register} (inc|dec) {number|register} if {number|register} (<|<=|=|!=|=>|>) {number|register}

What is the largest value in any register?

AoC 2017 Day 7: Tree

2017-12-07

Source: Recursive Circus

Part 1: A tree is defined as such:

node (weight) -> child1, child2, ...
node (weight)

Where a node always has a weight, but may or may not have child nodes.

What is the name of the root node of the tree (the node without a parent)?

AoC 2017 Day 6: Tightrope

2017-12-06

Source: Memory Reallocation

Part 1: Start with n stacks of different sizes. Take the largest block and distribute its items starting with n+1 and looping around. How many iterations of this does it take before you see a state you’ve seen before?

AoC 2017 Day 5: 21 Jump Street

2017-12-05

Source: A Maze of Twisty Trampolines, All Alike¹

Part 1: Interpret a program made entirely of jump instructions: each instruction is how many steps to jump. Any time you use an instruction to jump, increase the value of that jump by 1 for next time. How many total steps does it take to escape (jump out of bounds)?