Day 2 Part 1

day_2/.github/workflows/test.yml

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+name: test
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: erlef/setup-beam@v1
+        with:
+          otp-version: "28"
+          gleam-version: "1.13.0"
+          rebar3-version: "3"
+          # elixir-version: "1"
+      - run: gleam deps download
+      - run: gleam test
+      - run: gleam format --check src test

day_2/.gitignore

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+*.beam
+*.ez
+/build
+erl_crash.dump

day_2/README.md

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+# day_2
+
+[![Package Version](https://img.shields.io/hexpm/v/day_2)](https://hex.pm/packages/day_2)
+[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/day_2/)
+
+```sh
+gleam add day_2@1
+```
+```gleam
+import day_2
+
+pub fn main() -> Nil {
+  // TODO: An example of the project in use
+}
+```
+
+Further documentation can be found at <https://hexdocs.pm/day_2>.
+
+## Development
+
+```sh
+gleam run   # Run the project
+gleam test  # Run the tests
+```

day_2/gleam.toml

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+name = "day_2"
+version = "1.0.0"
+
+# Fill out these fields if you intend to generate HTML documentation or publish
+# your project to the Hex package manager.
+#
+# description = ""
+# licences = ["Apache-2.0"]
+# repository = { type = "github", user = "", repo = "" }
+# links = [{ title = "Website", href = "" }]
+#
+# For a full reference of all the available options, you can have a look at
+# https://gleam.run/writing-gleam/gleam-toml/.
+
+[dependencies]
+gleam_stdlib = ">= 0.44.0 and < 2.0.0"
+simplifile = ">= 2.3.1 and < 3.0.0"
+
+[dev-dependencies]
+gleeunit = ">= 1.0.0 and < 2.0.0"

day_2/input.txt

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+24-46,124420-259708,584447-720297,51051-105889,6868562486-6868811237,55-116,895924-1049139,307156-347325,372342678-372437056,1791-5048,3172595555-3172666604,866800081-866923262,5446793-5524858,6077-10442,419-818,57540345-57638189,2143479-2274980,683602048-683810921,966-1697,56537997-56591017,1084127-1135835,1-14,2318887654-2318959425,1919154462-1919225485,351261-558210,769193-807148,4355566991-4355749498,809094-894510,11116-39985,9898980197-9898998927,99828221-99856128,9706624-9874989,119-335

day_2/manifest.toml

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+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "filepath", version = "1.1.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "B06A9AF0BF10E51401D64B98E4B627F1D2E48C154967DA7AF4D0914780A6D40A" },
+  { name = "gleam_stdlib", version = "0.67.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "6368313DB35963DC02F677A513BB0D95D58A34ED0A9436C8116820BF94BE3511" },
+  { name = "gleeunit", version = "1.9.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "DA9553CE58B67924B3C631F96FE3370C49EB6D6DC6B384EC4862CC4AAA718F3C" },
+  { name = "simplifile", version = "2.3.1", build_tools = ["gleam"], requirements = ["filepath", "gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "957E0E5B75927659F1D2A1B7B75D7B9BA96FAA8D0C53EA71C4AD9CD0C6B848F6" },
+]
+
+[requirements]
+gleam_stdlib = { version = ">= 0.44.0 and < 2.0.0" }
+gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
+simplifile = { version = ">= 2.3.1 and < 3.0.0" }

day_2/src/day_2.gleam

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+import gleam/int
+import gleam/io
+import gleam/list
+import gleam/result
+import gleam/string
+import simplifile
+
+pub fn digits(x: Int, base: Int) -> Result(List(Int), Nil) {
+  case base < 2 {
+    True -> Error(Nil)
+    False -> Ok(digits_loop(x, base, []))
+  }
+}
+
+fn digits_loop(x: Int, base: Int, acc: List(Int)) -> List(Int) {
+  case int.absolute_value(x) < base {
+    True -> [x, ..acc]
+    False -> digits_loop(x / base, base, [x % base, ..acc])
+  }
+}
+
+pub fn int_to_half_length_pair(i: Int) -> Result(#(List(Int), List(Int)), Nil) {
+  digits(i, 10)
+  |> result.map(fn(l) { list.split(list: l, at: list.length(l) / 2) })
+}
+
+pub fn int_is_doubled_string(i: Int) -> Result(Bool, Nil) {
+  int_to_half_length_pair(i)
+  |> result.map(fn(p) {
+    let #(start, end) = p
+    start == end
+  })
+}
+
+pub fn filter_for_bad_ids(ids: List(Int)) -> List(Int) {
+  list.filter(ids, fn(id) { int_is_doubled_string(id) |> result.unwrap(False) })
+}
+
+pub fn ranges_to_list_of_ids(ids: List(#(Int, Int))) -> List(Int) {
+  list.map(ids, fn(id_pair) {
+    let #(first, last) = id_pair
+    list.range(first, last)
+  })
+  |> list.flatten
+}
+
+pub fn ranges_to_bad_ids(ids: List(#(Int, Int))) -> List(Int) {
+  ranges_to_list_of_ids(ids) |> filter_for_bad_ids
+}
+
+pub fn sum_of_bad_ids(ids: List(#(Int, Int))) -> Int {
+  ranges_to_bad_ids(ids) |> list.fold(0, int.add)
+}
+
+pub fn range_string_to_int_pair(s: String) -> #(Int, Int) {
+  let assert [a, b] =
+    string.split(s, on: "-")
+    |> list.map(int.parse)
+    |> list.map(result.unwrap(_, 0))
+  #(a, b)
+}
+
+pub fn list_of_ranges_to_int_pairs(s: String) -> List(#(Int, Int)) {
+  string.split(s, on: ",") |> list.map(range_string_to_int_pair)
+}
+
+pub fn file_to_sum_of_bad_ids(f: String) -> Int {
+  simplifile.read(f)
+  |> result.unwrap("")
+  |> string.trim
+  |> list_of_ranges_to_int_pairs
+  |> sum_of_bad_ids
+}
+
+pub fn main() -> Nil {
+  file_to_sum_of_bad_ids("input.txt") |> int.to_string |> io.println
+}

day_2/test/calibration.txt

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+11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124

day_2/test/day_2_test.gleam

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+import day_2
+import gleeunit
+
+pub fn main() -> Nil {
+  gleeunit.main()
+}
+
+pub fn trivial_digits_test() {
+  assert day_2.int_to_half_length_pair(1) == Ok(#([], [1]))
+}
+
+pub fn two_digit_number_test() {
+  assert day_2.int_to_half_length_pair(12) == Ok(#([1], [2]))
+}
+
+pub fn ten_digit_number_test() {
+  assert day_2.int_to_half_length_pair(1_234_567_890)
+    == Ok(#([1, 2, 3, 4, 5], [6, 7, 8, 9, 0]))
+}
+
+pub fn eleven_digit_number_test() {
+  assert day_2.int_to_half_length_pair(12_345_678_901)
+    == Ok(#([1, 2, 3, 4, 5], [6, 7, 8, 9, 0, 1]))
+}
+
+pub fn bad_number_test() {
+  assert day_2.int_is_doubled_string(123_123) == Ok(True)
+}
+
+pub fn good_number_test() {
+  assert day_2.int_is_doubled_string(123_456) == Ok(False)
+}
+
+pub fn list_of_ranges_test() {
+  assert day_2.ranges_to_list_of_ids([#(10, 20), #(30, 40)])
+    == [
+      10,
+      11,
+      12,
+      13,
+      14,
+      15,
+      16,
+      17,
+      18,
+      19,
+      20,
+      30,
+      31,
+      32,
+      33,
+      34,
+      35,
+      36,
+      37,
+      38,
+      39,
+      40,
+    ]
+}
+
+pub fn ranges_with_bad_ids_test() {
+  assert day_2.ranges_to_bad_ids([
+      #(11, 22),
+      #(95, 115),
+      #(998, 1012),
+      #(1_188_511_880, 1_188_511_890),
+      #(222_220, 222_224),
+      #(1_698_522, 1_698_528),
+      #(446_443, 446_449),
+      #(38_593_856, 38_593_862),
+    ])
+    == [11, 22, 99, 1010, 1_188_511_885, 222_222, 446_446, 38_593_859]
+}
+
+pub fn sum_of_bad_ids_test() {
+  assert day_2.sum_of_bad_ids([
+      #(11, 22),
+      #(95, 115),
+      #(998, 1012),
+      #(1_188_511_880, 1_188_511_890),
+      #(222_220, 222_224),
+      #(1_698_522, 1_698_528),
+      #(446_443, 446_449),
+      #(38_593_856, 38_593_862),
+    ])
+    == 1_227_775_554
+}
+
+pub fn range_parse_test() {
+  assert day_2.range_string_to_int_pair("111-333") == #(111, 333)
+}
+
+pub fn ranges_parse_test() {
+  let ranges =
+    "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124"
+  assert day_2.list_of_ranges_to_int_pairs(ranges)
+    == [
+      #(11, 22),
+      #(95, 115),
+      #(998, 1012),
+      #(1_188_511_880, 1_188_511_890),
+      #(222_220, 222_224),
+      #(1_698_522, 1_698_528),
+      #(446_443, 446_449),
+      #(38_593_856, 38_593_862),
+      #(565_653, 565_659),
+      #(824_824_821, 824_824_827),
+      #(2_121_212_118, 2_121_212_124),
+    ]
+}
+
+pub fn calibrate() {
+  assert day_2.file_to_sum_of_bad_ids("test/calibration.txt") == 1_227_775_554
+}