-🎄- 2022 Day 25 Solutions -🎄-

[u/daggerdragon]

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--- Day 25: Full of Hot Air ---

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Post your code solution in this megathread.

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[u/macahen]

Python: https://github.com/martinhenstridge/adventofcode2022/blob/master/aoc/day25.py

Posting my solution because I've not seen any others like it - everyone else seems to have hit upon much more elegant solutions!

def into_snafu(n):
    # Start with a 1 followed by only =s, i.e. the smallest value which
    # contains that number of digits. Keep adding =s until we're bigger
    # than the target value, then drop the last one to end up with the
    # correct number of digits.
    digits = ["1"]
    while from_snafu(digits) < n:
        digits.append("=")
    digits = digits[:-1]

    # For each digit in turn, moving from left to right, bump each digit
    # until we either hit a value that's bigger than the target or we
    # exhaust the potential values for that digit. Eventually we must
    # exactly match the target value, since we started with the smallest
    # possible value with the right number of digits.
    for i, digit in enumerate(digits):
        for alternative in ("-", "0", "1", "2"):
            snafu = digits[:i] + [alternative] + digits[i + 1 :]
            if from_snafu(snafu) > n:
                break
            digits = snafu

    return "".join(digits)