“Cephalopod math doesn’t look that different from normal math.”

Github: GCaggianese/AoC-2025/D6

Puzzle Day 6: Trash Compactor

Part One

• Parse the input as a matrix using spaces (“ “) as separators
• Do the operator operation (last row) to every column in the same row
• Sum the results.

Part 2

Part 2 requires reading the input numbers **vertically** instead of horizontally. Each column position becomes a digit, and digits stack top-to-bottom to form new numbers. Here is important to denote that there are spaces with the number inputs too (“ 51”) as an example, this matters as when reading vertically will change the indentation, therefore if it’s a part of another number or not.

Updated Parsing

1. Mantain the character positions
   • readdlm destroys spatial information by treating spaces as delimiters. → use readlines() and parse characters one by one.
2. Expand the header
   • The operators row uses spaces to mean “repeat previous operator”. So * + * + expands to ****++++****+++ → each column has its operator.
3. Read columns vertically
   • For each column position, stack the digits from all rows (top to bottom).
   • Concatenate them into a single number.
     • Spaces within the number grid mean “no digit here”.
4. Separator columns
   • A column whith all cells " " means a separator between operations.
5. Apply operators and sum
   • Group consecutive numbers between separators
   • Apply their operator
   • Sum all results for the answer.