day2: that one was hard

Author: keyboard-slayer

gleam.toml

@@ -14,6 +14,8 @@ version = "1.0.0"
 
 [dependencies]
 gleam_stdlib = ">= 0.34.0 and < 2.0.0"
+gleam_erlang = ">= 0.32.0 and < 1.0.0"
+simplifile = ">= 2.2.0 and < 3.0.0"
 
 [dev-dependencies]
 gleeunit = ">= 1.0.0 and < 2.0.0"

manifest.toml

@@ -2,10 +2,15 @@
 # You typically do not need to edit this file
 
 packages = [
+  { name = "filepath", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "67A6D15FB39EEB69DD31F8C145BB5A421790581BD6AA14B33D64D5A55DBD6587" },
+  { name = "gleam_erlang", version = "0.32.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "B18643083A0117AC5CFD0C1AEEBE5469071895ECFA426DCC26517A07F6AD9948" },
   { name = "gleam_stdlib", version = "0.45.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "206FCE1A76974AECFC55AEBCD0217D59EDE4E408C016E2CFCCC8FF51278F186E" },
   { name = "gleeunit", version = "1.2.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "F7A7228925D3EE7D0813C922E062BFD6D7E9310F0BEE585D3A42F3307E3CFD13" },
+  { name = "simplifile", version = "2.2.0", build_tools = ["gleam"], requirements = ["filepath", "gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "0DFABEF7DC7A9E2FF4BB27B108034E60C81BEBFCB7AB816B9E7E18ED4503ACD8" },
 ]
 
 [requirements]
+gleam_erlang = { version = ">= 0.32.0 and < 1.0.0" }
 gleam_stdlib = { version = ">= 0.34.0 and < 2.0.0" }
 gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
+simplifile = { version = ">= 2.2.0 and < 3.0.0" }

src/aoc_2024.gleam

@@ -1,7 +1,10 @@
 import day1
+import day2
 import gleam/io
 
 pub fn main() {
   io.println("===== Day 1 ======")
   day1.main()
+  io.println("===== Day 2 ======")
+  day2.main()
 }

src/d2input.txt

@@ -56,8 +56,6 @@ pub fn impl_p2(in: String) {
 }
 
 pub fn main() {
-  io.print("Part 1:   ")
   io.debug(impl_p1(d1input.get_input()))
-  io.print("Part 2:   ")
   io.debug(impl_p2(d1input.get_input()))
 }

src/day1.gleam

@@ -0,0 +1,78 @@
+import gleam/int
+import gleam/io
+import gleam/list
+import gleam/option
+import gleam/string
+import simplifile
+
+fn is_safe(x1: Int, x2: Int, inc: Bool) -> Bool {
+  let sum = x1 - x2
+  { inc && sum > 0 && sum <= 3 } || { !inc && sum < 0 && sum >= -3 }
+}
+
+fn solve(l: List(Int), inc: option.Option(Bool)) -> Bool {
+  case l {
+    [x1, x2, ..xs] -> {
+      let actual_inc = case inc {
+        option.None -> x1 - x2 > 0
+        option.Some(i) -> i
+      }
+      case is_safe(x1, x2, actual_inc) {
+        True -> solve([x2, ..xs], option.Some(actual_inc))
+        False -> False
+      }
+    }
+    _ -> True
+  }
+}
+
+pub fn impl_p1(in: String) -> Int {
+  string.split(in, on: "\n")
+  |> list.filter(fn(l) {
+    string.split(l, on: " ")
+    |> list.filter_map(int.parse)
+    |> solve(option.None)
+  })
+  |> list.count(fn(x) { !string.is_empty(x) })
+}
+
+fn dampen_loop(
+  l: List(Int),
+  acc: List(Int),
+  inc: option.Option(Bool),
+) -> List(Int) {
+  case l {
+    [x, ..xs] -> {
+      let newlst = list.append(list.reverse(acc), xs)
+      case solve(newlst, inc) {
+        True -> newlst
+        False -> dampen_loop(xs, [x, ..acc], inc)
+      }
+    }
+    [] -> list.reverse(acc)
+  }
+}
+
+fn dampen(l: List(Int), inc: option.Option(Bool)) -> List(Int) {
+  case solve(l, inc) {
+    True -> l
+    False -> dampen_loop(l, [], inc)
+  }
+}
+
+pub fn impl_p2(in: String) -> Int {
+  string.split(in, on: "\n")
+  |> list.filter(fn(l) {
+    string.split(l, on: " ")
+    |> list.filter_map(int.parse)
+    |> dampen(option.None)
+    |> solve(option.None)
+  })
+  |> list.count(fn(x) { !string.is_empty(x) })
+}
+
+pub fn main() {
+  let assert Ok(input) = simplifile.read("./src/d2input.txt")
+  io.debug(impl_p1(string.trim_end(input)))
+  io.debug(impl_p2(string.trim_end(input)))
+}

src/day2.gleam

@@ -2,6 +2,7 @@ import gleeunit
 import gleeunit/should
 
 import day1
+import day2
 
 pub fn main() {
   gleeunit.main()
@@ -19,3 +20,16 @@ pub fn day1_test() {
   day1.impl_p1(input) |> should.equal(11)
   day1.impl_p2(input) |> should.equal(31)
 }
+
+pub fn day2_test() {
+  let input =
+    "7 6 4 2 1
+  1 2 7 8 9
+  9 7 6 2 1
+  1 3 2 4 5
+  8 6 4 4 1
+  3 5 8 11 11 15
+  1 3 6 7 9"
+  day2.impl_p1(input) |> should.equal(2)
+  day2.impl_p2(input) |> should.equal(4)
+}