Solve part 1 of day 20

1 files changed, 17 insertions, 4 deletions

diff --git a/aoc-2020-gleam/src/ext/iteratorx.gleam b/aoc-2020-gleam/src/ext/iteratorx.gleam
index 0e59f17..6c7838d 100644
--- a/aoc-2020-gleam/src/ext/iteratorx.gleam
+++ b/aoc-2020-gleam/src/ext/iteratorx.gleam
@@ -1,3 +1,6 @@
+import gleam/int
+import gleam/result as res
+import gleam/dict.{type Dict}
 import gleam/iterator.{type Iterator, Next} as iter
 
 pub fn length(iterator: Iterator(a)) -> Int {
@@ -11,6 +14,19 @@ pub fn count(iterator: Iterator(a), satisfying predicate: fn(a) -> Bool) -> Int
   |> length
 }
 
+pub fn counts(iterator: Iterator(a)) -> Dict(a, Int) {
+  iterator
+  |> iter.fold(from: dict.new(), with: fn(acc, value) {
+    acc
+    |> dict.insert(
+      value,
+      dict.get(acc, value)
+      |> res.unwrap(or: 0)
+      |> int.add(1),
+    )
+  })
+}
+
 pub fn filter_map(
   iterator: Iterator(a),
   with mapper: fn(a) -> Result(b, c),
@@ -25,8 +41,5 @@ pub fn filter_map(
 }
 
 pub fn unfold_infinitely(from state: a, with fun: fn(a) -> a) -> Iterator(a) {
-  iter.unfold(
-    from: state,
-    with: fn(s) { Next(element: s, accumulator: fun(s)) },
-  )
+  iter.unfold(from: state, with: fn(s) { Next(element: s, accumulator: fun(s)) })
 }