Module day19

Linen Layout

Solves both parts simultaneously. Part one is the number of designs with non-zero possible combinations.

An elegant approach to check if the design starts with any towel is to first build a trie. Each node in the trie stores a bool indicating if it’s a valid towel and links to the next node for each possible color.

There are only 5 colors. A custom perfect hash function maps indices between 0 and 7 so that they fit into a fixed size array. This is faster than using a HashSet.

Additionally we store the Trie in a flat vec. This is simpler and faster than creating objects on the heap using Box.

Structs

• Node 🔒
  Simple Node object that uses indices to link to other nodes.

Functions

• parse
• part1
• part2
• perfect_hash 🔒
  Hashes the five possible color values white (w), blue (u), black (b), red (r), or green (g) to 0, 2, 4, 5 and 1 respectively. This compresses the range to fit into an array of 6 elements.

Type Aliases

• Input 🔒