From bc9ad3f333d4f6f72bb71c8c7dc9cf53ea0618f7 Mon Sep 17 00:00:00 2001
From: Pedro Correa <pedro8correa@gmail.com>
Date: Mon, 5 Jan 2026 15:11:16 -0300
Subject: [PATCH] :sparkles: (Gleam) aoc day 9

---
 src/day_09.gleam       | 53 ++++++++++++++++++++++++++++++++++++++++++
 test/day_09_test.gleam | 47 +++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 src/day_09.gleam
 create mode 100644 test/day_09_test.gleam

diff --git a/src/day_09.gleam b/src/day_09.gleam
new file mode 100644
index 0000000..8f22e48
--- /dev/null
+++ b/src/day_09.gleam
@@ -0,0 +1,53 @@
+import gleam/bool
+import gleam/int
+import gleam/list
+import gleam/pair
+import gleam/string
+
+type Coordinates =
+  List(#(Int, Int))
+
+pub fn format_input(input: String) -> Coordinates {
+  use line <- list.filter_map(input |> string.split("\n"))
+
+  use <- bool.guard(when: line == "", return: Error(""))
+
+  let assert [x, y] = line |> string.split(",")
+  let assert Ok(new_x) = int.parse(x)
+  let assert Ok(new_y) = int.parse(y)
+
+  Ok(#(new_x, new_y))
+}
+
+fn calculate_axis_distance(first: #(Int, Int), second: #(Int, Int)) {
+  fn(abs_function: fn(#(Int, Int)) -> Int) -> Int {
+    let pf = abs_function(first)
+    let ps = abs_function(second)
+
+    case pf > ps {
+      True -> pf - ps + 1
+      _ -> ps - pf + 1
+    }
+  }
+}
+
+fn calculate_distance(first: #(Int, Int), second: #(Int, Int)) -> Int {
+  let calculate_with_axis = calculate_axis_distance(first, second)
+
+  calculate_with_axis(pair.first) * calculate_with_axis(pair.second)
+}
+
+pub fn calculate_area(coordinates: Coordinates) -> Int {
+  coordinates
+  |> list.combination_pairs
+  |> list.fold(0, fn(acc, values) {
+    let #(first, second) = values
+
+    let value = calculate_distance(first, second)
+
+    case value > acc {
+      True -> value
+      _ -> acc
+    }
+  })
+}
diff --git a/test/day_09_test.gleam b/test/day_09_test.gleam
new file mode 100644
index 0000000..f6f934e
--- /dev/null
+++ b/test/day_09_test.gleam
@@ -0,0 +1,47 @@
+import day_09
+import simplifile
+
+pub fn read_file_test() {
+  assert "7,1
+11,1
+11,7
+9,7
+9,5
+2,5
+2,3
+7,3"
+    |> day_09.format_input
+    == [
+      #(7, 1),
+      #(11, 1),
+      #(11, 7),
+      #(9, 7),
+      #(9, 5),
+      #(2, 5),
+      #(2, 3),
+      #(7, 3),
+    ]
+}
+
+pub fn calculate_area_test() {
+  assert "7,1
+11,1
+11,7
+9,7
+9,5
+2,5
+2,3
+7,3"
+    |> day_09.format_input
+    |> day_09.calculate_area
+    == 50
+}
+
+pub fn calculate_distances_for_real_test() {
+  let assert Ok(file) = simplifile.read("input/day_09")
+
+  assert file
+    |> day_09.format_input
+    |> day_09.calculate_area
+    == 4_758_121_828
+}
-- 
2.51.2