Today was pretty cool, a bit similar to day 15 but...

# advent-of-code

[karelpeeters]

Today was pretty cool, a bit similar to day 15 but without a grid. I got a lot of use out of sortedBy, sumBy, filter, maxWith, takeIf etc! (spoiler in thread)

[karelpeeters]

Initially I didn't expect that some battles would get stuck, my code blocked and I was afraid there was a "real" bug simple smile

[Marcin Wisniowski]

Same, the stalemate got me by surprise. 😄

[stkent]

Ooh, yes, that was a good twist!

[stkent]

I used a sequence to dynamically ignore "recently-dead" groups while performing attacks; I think one of @todd.ginsberg's earlier solutions tipped me off as to that lazy trick! 👏

[stkent]

Much more satisfying day than 23 😄

[karelpeeters]

Can you show that sequence code?

[stkent]

val attackOrder = pendingAttacks
    .keys
    .sortedWith(compareByDescending(Group::initiative))

attackOrder
    .asSequence()
    .filterNot { it.size == 0 }
    .forEach { attacker ->
        pendingAttacks[attacker]?.let { target ->
            attacker.attack(target).also { unitsDied = unitsDied || it }
        }
    }

[stkent]

Note that target is mutated by the call to attack

[stkent]

But itself may also be present in attackOrder, and need to be skipped because all units died

[karelpeeters]

Ah that's neat.

[stkent]

Yeah, I remember liking it when I saw it so glad to have a chance to deploy 🙂