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import gary.{type ErlangArray}
import gary/array
import gleam/int
import gleam/list
import gleam/result
import gleam/string
pub fn parse(input: String) -> ErlangArray(Int) {
input
|> string.split("\n")
|> list.map(int.parse)
|> result.values()
|> array.from_list(default: 0)
|> array.make_fixed()
}
pub fn pt_1(input: ErlangArray(Int)) {
next_step(input, 0, 0, part: 1)
}
pub fn pt_2(input: ErlangArray(Int)) {
next_step(input, 0, 0, part: 2)
}
fn next_step(
instructions: ErlangArray(Int),
pointer: Int,
step: Int,
part part: Int,
) {
case array.get(from: instructions, at: pointer) {
Ok(distance) -> {
let delta = delta(distance, part)
let assert Ok(updated_instructions) =
array.set(instructions, at: pointer, put: distance + delta)
next_step(updated_instructions, pointer + distance, step + 1, part)
}
Error(_) -> step
}
}
fn delta(d: Int, part: Int) {
case part, d {
1, _ -> 1
_, n if n < 3 -> 1
_, _ -> -1
}
}
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