Day 2 Part 2

day_2/input02.txt

@@ -0,0 +1 @@
+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/src/day_2.gleam

@@ -1,6 +1,7 @@
 import gleam/int
 import gleam/io
 import gleam/list
+import gleam/pair
 import gleam/result
 import gleam/string
 import simplifile
@@ -32,6 +33,34 @@ pub fn int_is_doubled_string(i: Int) -> Result(Bool, Nil) {
   })
 }
 
+pub fn digits_to_substrings(i: List(Int)) -> List(List(Int)) {
+  list.map(i, fn(d) { [d] })
+  |> list.map_fold([], fn(acc, d) {
+    #(
+      list.append(acc, [list.append(list.last(acc) |> result.unwrap([]), d)]),
+      list.append(list.last(acc) |> result.unwrap([]), d),
+    )
+  })
+  |> pair.first
+  |> list.filter(fn(l) { l != i })
+}
+
+pub fn can_repeat_into(l: List(a), r: List(a)) -> Bool {
+  { list.length(r) % list.length(l) } == 0
+}
+
+pub fn repeats_into(s: List(Int), f: List(Int)) -> Bool {
+  list.repeat(s, { list.length(f) / list.length(s) }) |> list.flatten == f
+}
+
+pub fn has_repeated_string(i: Int) -> Bool {
+  let digits = digits(i, 10) |> result.unwrap([])
+  digits_to_substrings(digits)
+  |> list.filter(can_repeat_into(_, digits))
+  |> list.filter(repeats_into(_, digits))
+  |> fn(l) { l != [] }
+}
+
 pub fn filter_for_bad_ids(ids: List(Int)) -> List(Int) {
   list.filter(ids, fn(id) { int_is_doubled_string(id) |> result.unwrap(False) })
 }
@@ -72,6 +101,27 @@ pub fn file_to_sum_of_bad_ids(f: String) -> Int {
   |> sum_of_bad_ids
 }
 
-pub fn main() -> Nil {
+pub fn sum_of_bad_ids_part2(ids: List(#(Int, Int))) -> Int {
-  file_to_sum_of_bad_ids("input.txt") |> int.to_string |> io.println
+  ranges_to_bad_ids_part2(ids) |> list.fold(0, int.add)
+}
+
+pub fn file_to_sum_of_bad_ids_part2(f: String) -> Int {
+  simplifile.read(f)
+  |> result.unwrap("")
+  |> string.trim
+  |> list_of_ranges_to_int_pairs
+  |> sum_of_bad_ids_part2
+}
+
+pub fn ranges_to_bad_ids_part2(ids: List(#(Int, Int))) -> List(Int) {
+  ranges_to_list_of_ids(ids) |> filter_for_bad_ids_part2
+}
+
+pub fn filter_for_bad_ids_part2(ids: List(Int)) -> List(Int) {
+  list.filter(ids, fn(id) { has_repeated_string(id) })
+}
+
+pub fn main() -> Nil {
+  // file_to_sum_of_bad_ids("input.txt") |> int.to_string |> io.println
+  file_to_sum_of_bad_ids_part2("input02.txt") |> int.to_string |> io.println
 }

day_2/test/day_2_test.gleam

@@ -110,6 +110,43 @@ pub fn ranges_parse_test() {
     ]
 }
 
-pub fn calibrate() {
+pub fn calibrate_test() {
   assert day_2.file_to_sum_of_bad_ids("test/calibration.txt") == 1_227_775_554
 }
+
+pub fn int_to_substrings_test() {
+  assert day_2.digits_to_substrings([1, 2, 3, 4]) == [[1], [1, 2], [1, 2, 3]]
+}
+
+pub fn can_repeat_into_test() {
+  assert day_2.can_repeat_into([1, 2], [1, 2, 3, 4])
+}
+
+pub fn cannot_repeat_into_test() {
+  assert !{ day_2.can_repeat_into([1, 2], [1, 2, 3]) }
+}
+
+pub fn repeats_into_test() {
+  assert day_2.repeats_into([1, 2], [1, 2, 1, 2])
+}
+
+pub fn doesnot_repeat_into_test() {
+  assert !day_2.repeats_into([1, 2], [1, 2, 3])
+}
+
+pub fn has_doubled_string_test() {
+  assert day_2.has_repeated_string(1212)
+}
+
+pub fn has_trippled_string_test() {
+  assert day_2.has_repeated_string(121_212)
+}
+
+pub fn no_repeated_strings_test() {
+  assert !day_2.has_repeated_string(123)
+}
+
+pub fn calibrate_part2_test() {
+  assert day_2.file_to_sum_of_bad_ids_part2("test/calibration.txt")
+    == 4_174_379_265
+}