Module day15 

Warehouse Woes

Festive version of Sokoban.

Part one loops in a straight line looking for the next space . or wall #. No bounds checks are needed as the maze is enclosed. If a space is found then all items are pushed one block in that direction.

Part two re-uses the part one logic for horizontal moves. Vertical moves use a breadth-first search to identify the cascading boxes that need to be moved. Boxes are added strictly left to right to make checking for previously added boxes easier. To prevent adding a box twice we check that the item at index - 2 is different. For example:

    @          Indices:
    []         23
   [][]       4567
    []         89

When processing 6 we try to add 8, however 8 and 9 have already been added when processing 4 so we skip.

If any next space is a wall then we cancel the entire move and return right away. Otherwise all boxes are moved in the reverse order that they were found by the search.

Functions

gps 🔒

narrow 🔒

parse

part1

part2

stretch 🔒

wide 🔒

Type Aliases

Input 🔒