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Cover image for Advent of Code 2019 Solution Megathread - Day 25: Cryostasis

Advent of Code 2019 Solution Megathread - Day 25: Cryostasis

jbristow profile image Jon Bristow ・2 min read

Merry Christmas!

Day 25 - The Problem

We made it to Santa's location! Woo!

Hmm, maybe my celebratory dance was a little premature. Everything is too quiet.

Also really cold.

Since it's too dangerous, let's boot up our IntCode computer one last time as a live droid control interface and inspect the conditions of Santa's ship.

That's right, Part 1 (if you're not cheating, which is its own reward) is using our IntCode computers to play a Zork clone to navigate the ship, collect items, and bypass the weight checking security checkpoint.

Once we get the password to get on board, Santa greets us and requests 49 stars to re-calibrate the ship. Part 2 only requires that you complete all the other days with 2 stars.

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Jon Bristow Author

I didn't actually write more than a handful of lines of new code!

Mostly, I just reused the breakout clone (ascii output to screen) and added a blocking stdin read in the "input" section.

private fun Cryostasis.sendInput(): Cryostasis {
    return state.fold(
        ifLeft = { this },
        ifRight = {
            when {
                it.waitingForInput -> {
                    if (initalCommands.isNotEmpty()) {
                        it.inputs.addAll(initalCommands.pop().map(Char::toLong))
                    } else {
                        val enteredString = readLine()
                        it.inputs.addAll(enteredString!!.map(Char::toLong))
                        it.inputs.add(10L)
                    }
                    this.copy(saveState = code.toMap())
                }
                else -> {
                    this
                }
            }
        }
    )
}

As you can see, after game-overing myself a few times (Eaten by a grue! You'd think I'd learn after all these years!) I found it necessary to pipe in a pre-formatted set of inputs to bootstrap me back to the state I was in before.

I played around trying to see if there was an obvious way to cheat, but in the end I just wandered around and then did a manual DFS of the items to get my way through the security checkpoint.

Merry Christmas everyone! Thanks for sharing your work with me! I hope you had fun!

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Jon Bristow Author

Here's a rudimentary map I made in excel: i.imgur.com/hW2bFJw.png