2023 Day 11: Cosmic Expansion

What a relief after yesterday’s puzzle!

  • Kind of amusing how the puzzle master attempted to disguise Manhattan distance. I recently completed the 2018 puzzles, and he made no attempt to disguise that.
  • It amuses me that I guessed Part 2’s task while completing Part 1, so I went ahead and solved Part 1 with an approach that made it easy to complete Part 2 in about 5 minutes. The puzzle master’s love of throwing huge numbers into puzzles, which blocks a lot of obvious approaches, really helped foresee where this was going.
  • That 5 minutes for Part 2 includes the minute I spent figuring out why my initial answer was wrong… for each empty row or column between the galaxies, add 1 less than the number of rows.