4 ms·

Sure I have a "live" example in my 2024 AoC code. I'll add it here when I get home.

• ColinWright 2y ago
  Fabulous ... thanks. I've bookmarked this bit of the thread so I can come back and check it. Cheers!
  • reedf1 2y ago
    Hi - for https://adventofcode.com/2024/day/5 https://adventofcode.com/2024/day/5 (Part 2): instructions = [] updates = [] with open("input.txt") as file: for line in file: line = line.rstrip() if line == "": break x, y = line.split('|') instructions.append((int(x), int(y))) for line in file: line = line.rstrip() pages = [int(i) for i in line.split(',')] updates.append(pages) def is_valid_update(update, instructions): pos = {num: idx for idx, num in enumerate(update)} for x, y in instructions: if x in pos and y in pos and pos[x] > pos[y]: return False return True valid_updates = [upd for upd in updates if is_valid_update(upd, instructions)] accum_valid = sum(upd[len(upd) // 2] for upd in valid_updates) print("Sum from valid updates:", accum_valid) def domain_sort(update, instructions): n = len(update) for i in range(n): for j in range(n): if (update[j], update[i]) in instructions: update[i], update[j] = update[j], update[i] return update invalid_updates = [upd for upd in updates if not is_valid_update(upd, instructions)] sorted_updates = [domain_sort(upd.copy(), instructions) for upd in invalid_updates] print("Sorted invalid updates:") for upd in sorted_updates: print(upd) accum_sorted = sum(upd[len(upd) // 2] for upd in sorted_updates) print("Sum from sorted invalid updates:", accum_sorted)
    • ColinWright 2y ago
      Gosh, I never thought I'd see this "in the wild"! I would have a hard time understanding why this finishes with the "updates" in the order expected instead of the opposite order, and I'm intrigued. In the paper it just seems to counter-intuitive to me that if the comparison is that way round then the items get swapped ... if I found this in code I was auditing then I'd spent a long time trying to work out what was going on. Thank you.
      • reedf1 2y ago
        Yes, not something I would write in production code. But very easy for me to think about in a stream of consciousness. Usually I complete the above challenges in about 5-10mins.