Module day13

Transparent Origami

There are 2 possible approaches to tracking the position of dots after each fold:

• A HashSet that will collapse duplicate entries
• An array of sufficient dimensions to track every possible coordinate.

We will use both approaches for speed, the first in part 1 and the second in part 2.

For part 2 we can determine the final size of the paper by taking the last x and y coordinates from the fold instructions. It’s then faster and more convenienent to process each point completely and update the final location, than to step through intermediate folds.

Structs

Input

Enums

Fold

Functions

fold_horizontal 🔒

Fold point at x coordinate, doing nothing if the point is to the left of the fold line.

fold_vertical 🔒

Fold point at y coordinate, doing nothing if the point is above the fold line.

parse

Parse the input into collections of Point and Fold structs.

part1

Fold once then count dots. The sample data folds along y and my input folded along x testing both possibilities.

part2

Decode secret message.