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|
import gleam/int
import gleam/list
import glearray
pub fn parse(input: String) {
let assert Ok(n) = int.parse(input)
n
}
pub fn pt_1(input: Int) {
let assert [_, result] =
next_spin([0], 0, 1, input)
|> list.drop_while(fn(x) { x != 2017 })
|> list.take(2)
result
}
fn next_spin(list: List(Int), position: Int, cycle: Int, step: Int) {
case cycle {
2018 -> list
_ -> {
let next_position = { position + step } % cycle + 1
next_spin(
insert_at(list, next_position, cycle),
next_position,
cycle + 1,
step,
)
}
}
}
fn insert_at(xs: List(a), at index: Int, insert new: a) {
let #(left, right) = list.split(xs, index)
list.concat([left, [new], right])
}
pub fn pt_2(input: Int) {
next_spin_tracking_zero(0, 0, 1, input)
}
fn next_spin_tracking_zero(acc: Int, position: Int, cycle: Int, step: Int) {
case cycle {
50_000_001 -> acc
_ -> {
let next_position = { position + step } % cycle + 1
let next_acc = case next_position {
1 -> cycle
_ -> acc
}
next_spin_tracking_zero(next_acc, next_position, cycle + 1, step)
}
}
}
|
