Finish day 13

1 files changed, 21 insertions, 0 deletions

diff --git a/aoc-2020-gleam/src/ext/intx.gleam b/aoc-2020-gleam/src/ext/intx.gleam
index 9f06850..077b4f2 100644
--- a/aoc-2020-gleam/src/ext/intx.gleam
+++ b/aoc-2020-gleam/src/ext/intx.gleam
@@ -1,3 +1,24 @@
+import gleam/int
+import gleam/order.{Eq, Gt, Lt}
+
 pub fn is_between(number: Int, min: Int, and max: Int) {
   min <= number && number <= max
 }
+
+pub fn ceil_divide(dividend: Int, by divisor: Int) -> Int {
+  { dividend + divisor - 1 } / divisor
+}
+
+fn gcd(a: Int, b: Int) -> Int {
+  case b == 0 {
+    True -> a
+    False -> gcd(b, a % b)
+  }
+}
+
+pub fn lcm(a: Int, b: Int) -> Int {
+  case int.compare(a, b) {
+    Gt | Eq -> { a / gcd(a, b) } * b
+    Lt -> { b / gcd(a, b) } * a
+  }
+}