For those of you who write up utility functions, w...

# advent-of-code

[Neil Banman]

For those of you who write up utility functions, which are your favorites? Mine is:
fun String.getInts(): Sequence<Int>, which finds all the Ints in a String. Perfect for quick parsing of so many AoC inputs. Day4 uses line.getInts().drop(1). Often you don't need to even split your input into lines, just run getInts().chunked(n, ::transform).

[Neil Banman]

The version I use is found here, but is a little too generalized for quick inspection. A perfectly usable version can be done in two lines:

private val intRx = Regex("""(?<!\d)-?\d+""")
fun String.getInts() = intRx.findAll(this).mapNotNull { it.value.toIntOrNull() }

[phldavies]

I tend to use

fun String.splitIntsNotNull(vararg delimiters: String = arrayOf(" ")) = split(*delimiters).mapNotNull(String::toIntOrNull)

[Pawel Matysek]

after today’s input my favourite is fun List<String>.chunkedByEmptyLine()

[Neil Banman]

Yeah, I combined those two for today's puzzle.

[Andrei Kovalevsky]

In day 4 I was using

val (id, a, b) = card.findIntNumbers().splitBy(setOf(1, 11))

[Neil Banman]

what does splitBy look like? Are you hardcoding the number of digits to split at?

[Andrei Kovalevsky]

fun <T> List<T>.splitBy(idx: Set<Int>) = foldIndexed(mutableListOf<MutableList<T>>()) { i, list, v ->
    if (idx.contains(i) || list.isEmpty()) list.add(mutableListOf(v)) else list.last().add(v)
    list
}