Day 4 part 1

2022/src/days/day_4.gleam

@@ -0,0 +1,45 @@
+import gleam/int
+import gleam/list.{map}
+import gleam/iterator
+import gleam/string
+
+type Range {
+  Range(start: Int, end: Int)
+}
+
+pub fn pt_1(input: String) -> Int {
+  string.split(input, on: "\n")
+  |> iterator.from_list
+  |> iterator.map(parse_line)
+  |> iterator.filter(fully_contains)
+  |> iterator.fold(0, fn(sum, _) { sum + 1 })
+}
+
+pub fn pt_2(input: String) -> Int {
+  todo
+}
+
+fn parse_line(line: String) -> #(Range, Range) {
+  assert [a, b] =
+    string.split(line, ",")
+    |> map(parse_range)
+  #(a, b)
+}
+
+fn parse_range(str: String) -> Range {
+  assert [start, end] =
+    string.split(str, "-")
+    |> map(parse_int)
+  Range(start, end)
+}
+
+fn parse_int(str: String) -> Int {
+  assert Ok(i) = int.parse(str)
+  i
+}
+
+fn fully_contains(pair: #(Range, Range)) -> Bool {
+  let a = pair.0
+  let b = pair.1
+  b.start >= a.start && b.end <= a.end || a.start >= b.start && a.end <= b.end
+}