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import adglent.{First, Second}
import gleam/io
import gleam/string
import gleam/result
import gleam/list.{Continue, Stop}
import gleam/int
import gleam/function
// Types -------------------------------------------------------------------------------------------
pub type Almanac {
Almanac(seeds: List(Int), mappers: List(Mapper))
}
pub type MappingRange {
MRange(start: Int, end: Int, offset: Int)
}
pub type SeedRange {
SRange(start: Int, end: Int)
}
type Mapper =
List(MappingRange)
// Parsing -----------------------------------------------------------------------------------------
fn parse_input(input: String) {
let assert ["seeds: " <> raw_seeds, ..raw_mappers] =
string.split(input, on: "\n\n")
let seeds = string_to_int_list(raw_seeds)
let mappers =
list.map(
raw_mappers,
function.compose(string.split(_, on: "\n"), parse_mapper),
)
Almanac(seeds, mappers)
}
fn string_to_int_list(str: String) {
str
|> string.split(on: " ")
|> list.map(int.parse)
|> result.values
}
fn parse_mapper(strs: List(String)) -> Mapper {
let assert [_, ..raw_ranges] = strs
list.map(raw_ranges, parse_mrange)
|> list.sort(fn(a, b) { int.compare(a.start, b.start) })
}
fn parse_mrange(str: String) -> MappingRange {
let assert [destination, source, range_width] = string_to_int_list(str)
MRange(source, source + range_width - 1, destination - source)
}
// Part 1 ------------------------------------------------------------------------------------------
pub fn part1(input: String) {
let Almanac(seeds, mappers) = parse_input(input)
list.map(seeds, list.fold(over: mappers, from: _, with: correspond))
|> list.reduce(int.min)
|> result.unwrap(0)
|> string.inspect
}
fn correspond(n: Int, mapper: Mapper) {
use acc, mrange <- list.fold_until(over: mapper, from: n)
case mrange.start <= acc && acc <= mrange.end {
True -> Stop(acc + mrange.offset)
False -> Continue(acc)
}
}
// Part 2 ------------------------------------------------------------------------------------------
pub fn part2(input: String) {
let Almanac(seeds, mappers) = parse_input(input)
let assert [SRange(answer, _), ..] =
seeds
|> list.sized_chunk(into: 2)
|> list.map(fn(chunk) {
let assert [start, length] = chunk
[SRange(start, start + length - 1)]
|> remap_all_seed_ranges(mappers)
})
|> list.flatten()
|> list.sort(fn(a, b) { int.compare(a.start, b.start) })
string.inspect(answer)
}
fn remap_all_seed_ranges(srs: List(SeedRange), mappers: List(Mapper)) {
case mappers {
[] -> srs
[mapper, ..rest] ->
list.flat_map(srs, remap_range(_, mapper))
|> remap_all_seed_ranges(rest)
}
}
fn remap_range(r: SeedRange, mapper: Mapper) -> List(SeedRange) {
do_remap_range(r, mapper, [])
}
fn transform_range(r: SeedRange, mapper: MappingRange) -> SeedRange {
SRange(r.start + mapper.offset, r.end + mapper.offset)
}
fn do_remap_range(r: SeedRange, mapper: Mapper, acc: List(SeedRange)) {
case mapper {
// no more mappings -> no mapping covers this range
[] -> [r, ..acc]
// range is to the left of current mapping -> no mapping covers this range
[m, ..] if r.end < m.start -> [r, ..acc]
// range is to the right of current mapping -> move to next mapping
[m, ..ms] if r.start > m.end -> do_remap_range(r, ms, acc)
// range is fully inside mapping -> range is transformed
[m, ..] if r.start >= m.start && r.end <= m.end -> [
transform_range(r, m),
..acc
]
// range overlaps start but not end -> left side not transformed, right side transformed
[m, ..] if r.start < m.start && r.end <= m.end -> [
SRange(r.start, m.start - 1),
transform_range(SRange(m.start, r.end), m),
..acc
]
// range overlaps end but not start -> left side transformed, right side moves to next mapping
[m, ..ms] if r.start >= m.start && r.end > m.end ->
do_remap_range(SRange(m.end + 1, r.end), ms, [
transform_range(SRange(r.start, m.end), m),
..acc
])
// mapping is fully inside range -> left not transformed, middle transformed, right to next
[m, ..ms] ->
do_remap_range(SRange(m.end + 1, r.end), ms, [
SRange(r.start, m.start - 1),
transform_range(SRange(m.start, m.end), m),
..acc
])
}
}
pub fn main() {
let assert Ok(part) = adglent.get_part()
let assert Ok(input) = adglent.get_input("5")
case part {
First ->
part1(input)
|> adglent.inspect
|> io.println
Second ->
part2(input)
|> adglent.inspect
|> io.println
}
}
|
