day 7

sample/day7-sample.txt

@@ -0,0 +1,9 @@
+190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20

src/day7_p1.gleam

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+import gleam/int
+import gleam/io
+import gleam/iterator
+import gleam/list.{Continue, Stop, count, filter, fold, map}
+import gleam/pair
+import gleam/result
+import gleam/string
+import stdin.{stdin}
+
+pub fn main() {
+  stdin()
+  |> read_input
+  |> filter(is_valid)
+  |> map(pair.first)
+  |> fold(0, int.add)
+  |> io.debug
+}
+
+fn is_valid(equation: #(Int, List(Int))) -> Bool {
+  let assert #(total, [base, ..operands]) = equation
+  let op_size = list.length(operands)
+  let limit = int.bitwise_shift_left(1, op_size)
+
+  list.range(0, limit)
+  |> list.any(fn(index) {
+    let operations =
+      index
+      |> int.to_base2
+      |> string.pad_start(to: op_size, with: "0")
+      |> string.to_graphemes
+
+    list.zip(operands, operations)
+    |> list.fold(base, fn(acc, op) {
+      let #(num, operation) = op
+      case operation {
+        "0" -> acc + num
+        "1" -> acc * num
+        _ -> panic as "unreachable"
+      }
+    })
+    |> fn(x) { x == total }
+  })
+}
+
+fn read_input(it: iterator.Iterator(String)) -> List(#(Int, List(Int))) {
+  it
+  |> iterator.to_list
+  |> map(string.trim)
+  |> filter(not(string.is_empty))
+  |> map(parse_line)
+}
+
+fn parse_line(line: String) -> #(Int, List(Int)) {
+  let assert Ok(#(total_str, ops_str)) = line |> string.split_once(":")
+  let assert Ok(total) = total_str |> int.parse
+  let assert Ok(ops) =
+    ops_str
+    |> string.trim
+    |> string.split(" ")
+    |> map(int.parse)
+    |> result.all
+
+  #(total, ops)
+}
+
+fn not(a: fn(a) -> Bool) {
+  fn(param: a) -> Bool { !a(param) }
+}

src/day7_p2.gleam

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+import gleam/float
+import gleam/int
+import gleam/io
+import gleam/iterator
+import gleam/list.{Continue, Stop, count, filter, fold, map}
+import gleam/pair
+import gleam/result
+import gleam/string
+import stdin.{stdin}
+
+pub fn main() {
+  stdin()
+  |> read_input
+  |> filter(is_valid)
+  |> map(pair.first)
+  |> fold(0, int.add)
+  |> io.debug
+}
+
+fn is_valid(equation: #(Int, List(Int))) -> Bool {
+  let assert #(total, [base, ..operands]) = equation
+  let op_size = list.length(operands)
+  let assert Ok(limit) =
+    int.power(3, of: op_size |> int.to_float) |> result.map(float.round)
+
+  list.range(0, limit)
+  |> list.any(fn(index) {
+    let assert Ok(operation_string) =
+      index
+      |> int.to_base_string(3)
+
+    let operations =
+      operation_string
+      |> string.pad_start(to: op_size, with: "0")
+      |> string.to_graphemes
+
+    list.zip(operands, operations)
+    |> list.fold(base, fn(acc, op) {
+      let #(num, operation) = op
+      case operation {
+        "0" -> acc + num
+        "1" -> acc * num
+        "2" -> concat(acc, num)
+        _ -> panic as "unreachable"
+      }
+    })
+    |> fn(x) { x == total }
+  })
+}
+
+fn concat(x: Int, y: Int) -> Int {
+  let assert Ok(x_digits) = int.digits(x, 10)
+  let assert Ok(y_digits) = int.digits(y, 10)
+
+  let assert Ok(num) = [x_digits, y_digits] |> list.flatten |> int.undigits(10)
+  num
+}
+
+fn read_input(it: iterator.Iterator(String)) -> List(#(Int, List(Int))) {
+  it
+  |> iterator.to_list
+  |> map(string.trim)
+  |> filter(not(string.is_empty))
+  |> map(parse_line)
+}
+
+fn parse_line(line: String) -> #(Int, List(Int)) {
+  let assert Ok(#(total_str, ops_str)) = line |> string.split_once(":")
+  let assert Ok(total) = total_str |> int.parse
+  let assert Ok(ops) =
+    ops_str
+    |> string.trim
+    |> string.split(" ")
+    |> map(int.parse)
+    |> result.all
+
+  #(total, ops)
+}
+
+fn not(a: fn(a) -> Bool) {
+  fn(param: a) -> Bool { !a(param) }
+}