day 7 complete

2 files changed, 185 insertions, 0 deletions

diff --git a/aoc2023/src/day7/.gitignore b/aoc2023/src/day7/.gitignore
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+++ b/aoc2023/src/day7/.gitignore
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+input.txt
\ No newline at end of file
diff --git a/aoc2023/src/day7/solve.gleam b/aoc2023/src/day7/solve.gleam
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+++ b/aoc2023/src/day7/solve.gleam
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+import adglent.{First, Second}
+import gleam/bool
+import gleam/function
+import gleam/int
+import gleam/io
+import gleam/list
+import gleam/order.{type Order, Eq, Lt}
+import gleam/string
+
+// Types -------------------------------------------------------------------------------------------
+
+type Hand {
+  Hand(cards: List(Int), wager: Int)
+}
+
+type HandType {
+  FiveOfAKind
+  FourOfAKind
+  FullHouse
+  ThreeOfAKind
+  TwoPair
+  OnePair
+  HighCard
+  Unknown
+}
+
+// Common functions --------------------------------------------------------------------------------
+
+fn hand_rank(hand_rank: HandType) -> Int {
+  case hand_rank {
+    HighCard -> 1
+    OnePair -> 2
+    TwoPair -> 3
+    ThreeOfAKind -> 4
+    FullHouse -> 5
+    FourOfAKind -> 6
+    FiveOfAKind -> 7
+    Unknown -> 100
+  }
+}
+
+fn card_rank(card: String) -> Int {
+  case int.parse(card), card {
+    Ok(n), _ -> n
+    _, "A" -> 14
+    _, "K" -> 13
+    _, "Q" -> 12
+    _, "J" -> 11
+    _, "T" -> 10
+    _, "*" -> 1
+  }
+}
+
+fn parse_hand(str: String) -> Hand {
+  let [cards, wager] = string.split(str, " ")
+  let cards =
+    string.to_graphemes(cards)
+    |> list.map(card_rank)
+  let assert Ok(wager) = int.parse(wager)
+
+  Hand(cards, wager)
+}
+
+fn card_counts(hand: Hand) {
+  hand.cards
+  |> list.sort(int.compare)
+  |> list.chunk(function.identity)
+  |> list.map(list.length)
+  |> list.sort(int.compare)
+}
+
+fn classify_hand(hand: Hand) -> HandType {
+  case list.length(list.unique(hand.cards)), card_counts(hand) {
+    1, _ -> FiveOfAKind
+    2, [1, 4] -> FourOfAKind
+    2, [2, 3] -> FullHouse
+    3, [1, 1, 3] -> ThreeOfAKind
+    3, [1, 2, 2] -> TwoPair
+    4, _ -> OnePair
+    5, _ -> HighCard
+    _, _ -> Unknown
+  }
+}
+
+// Part 1 ------------------------------------------------------------------------------------------
+
+pub fn part1(input: String) {
+  input
+  |> string.split("\n")
+  |> list.map(parse_hand)
+  |> list.sort(compare_hands)
+  |> list.index_map(fn(i, h) { { i + 1 } * h.wager })
+  |> int.sum
+  |> string.inspect
+}
+
+fn compare_hands(hand1: Hand, hand2: Hand) -> Order {
+  case
+    int.compare(
+      hand_rank(classify_hand(hand1)),
+      hand_rank(classify_hand(hand2)),
+    )
+  {
+    Eq -> compare_top_card(hand1.cards, hand2.cards)
+    other -> other
+  }
+}
+
+fn compare_top_card(cards1: List(Int), cards2: List(Int)) -> Order {
+  use <- bool.guard(cards1 == [] || cards2 == [], Eq)
+  let [c1, ..rest1] = cards1
+  let [c2, ..rest2] = cards2
+  case int.compare(c1, c2) {
+    Eq -> compare_top_card(rest1, rest2)
+    other -> other
+  }
+}
+
+// Part 2 ------------------------------------------------------------------------------------------
+
+pub fn part2(input: String) {
+  input
+  |> string.replace("J", "*")
+  |> string.split("\n")
+  |> list.map(parse_hand)
+  |> list.sort(compare_hands_considering_jokers)
+  |> list.index_map(fn(i, h) { { i + 1 } * h.wager })
+  |> int.sum
+  |> string.inspect
+}
+
+const card_subs = [2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14]
+
+fn find_best_joker_substitution(hand: Hand) {
+  use acc, card <- list.fold(card_subs, Hand([2, 3, 4, 5, 6], 0))
+  let subbed_cards =
+    list.map(
+      hand.cards,
+      fn(c) {
+        case c {
+          1 -> card
+          other -> other
+        }
+      },
+    )
+  let subbed_hand = Hand(..hand, cards: subbed_cards)
+  case compare_hands(acc, subbed_hand) {
+    Lt -> subbed_hand
+    _ -> acc
+  }
+}
+
+fn compare_hands_considering_jokers(hand1: Hand, hand2: Hand) -> Order {
+  case
+    int.compare(
+      hand1
+      |> find_best_joker_substitution
+      |> classify_hand
+      |> hand_rank,
+      hand2
+      |> find_best_joker_substitution
+      |> classify_hand
+      |> hand_rank,
+    )
+  {
+    Eq -> compare_top_card(hand1.cards, hand2.cards)
+    other -> other
+  }
+}
+
+pub fn main() {
+  let assert Ok(part) = adglent.get_part()
+  let assert Ok(input) = adglent.get_input("7")
+  case part {
+    First ->
+      part1(input)
+      |> adglent.inspect
+      |> io.println
+    Second ->
+      part2(input)
+      |> adglent.inspect
+      |> io.println
+  }
+}