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authorH.J <thechairman@thechairman.info>2024-10-09 11:36:55 -0400
committerH.J <thechairman@thechairman.info>2024-10-09 11:36:55 -0400
commit8777ff071f7bb37631baa7b6717ad29961e50911 (patch)
tree6d59c4ed58e454b960339c3d1151f0a879e8d7cb /gleam/aoc2023/src/day11/solve.gleam
parent6156a9ef7be4012063a042aafb4e9b0d7eadde8e (diff)
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+import adglent.{First, Second}
+import gleam/io
+import gleam/int
+import gleam/string
+import gleam/list
+
+type Posn {
+ Posn(x: Int, y: Int)
+}
+
+fn find_empty(grid: List(List(String))) {
+ use acc, row, r <- list.index_fold(grid, [])
+ case list.unique(row) {
+ ["."] -> [r, ..acc]
+ _ -> acc
+ }
+}
+
+fn count_prior_empty_ranks(rank: Int, empty_ranks: List(Int)) -> Int {
+ empty_ranks
+ |> list.drop_while(fn(r_empty) { r_empty > rank })
+ |> list.length
+}
+
+fn parse_with_expansion(input: String, expansion: Int) -> List(Posn) {
+ let add = expansion - 1
+ let grid =
+ input
+ |> string.split("\n")
+ |> list.map(string.to_graphemes)
+
+ let empty_row_list = find_empty(grid)
+ let empty_col_list = find_empty(list.transpose(grid))
+
+ {
+ use r, row <- list.index_map(grid)
+ use acc, cell, c <- list.index_fold(over: row, from: [])
+
+ let p = Posn(r, c)
+ let empty_r = count_prior_empty_ranks(r, empty_row_list)
+ let empty_c = count_prior_empty_ranks(c, empty_col_list)
+ case cell {
+ "#" -> [Posn(p.x + empty_r * add, p.y + empty_c * add), ..acc]
+ _empty -> acc
+ }
+ }
+ |> list.flatten()
+}
+
+fn all_distances(stars: List(Posn)) -> Int {
+ use acc, pair <- list.fold(list.combination_pairs(stars), 0)
+ let #(s1, s2) = pair
+ acc + int.absolute_value(s1.x - s2.x) + int.absolute_value(s1.y - s2.y)
+}
+
+fn find_distances(input: String, expand_by: Int) -> String {
+ input
+ |> parse_with_expansion(expand_by)
+ |> all_distances
+ |> string.inspect
+}
+
+pub fn part1(input: String) {
+ find_distances(input, 2)
+}
+
+pub fn part2(input: String) {
+ find_distances(input, 1_000_000)
+}
+
+pub fn main() {
+ let assert Ok(part) = adglent.get_part()
+ let assert Ok(input) = adglent.get_input("11")
+ case part {
+ First ->
+ part1(input)
+ |> adglent.inspect
+ |> io.println
+ Second ->
+ part2(input)
+ |> adglent.inspect
+ |> io.println
+ }
+}