Day 2 part 2

2022/src/days/day_2.gleam

@@ -8,9 +8,18 @@ type Hand {
   Scissors
 }
 
+type Outcome {
+  Lose
+  Draw
+  Win
+}
+
 type Game =
   #(Hand, Hand)
 
+type RiggedGame =
+  #(Hand, Outcome)
+
 pub fn pt_1(input: String) -> Int {
   string.split(input, on: "\n")
   |> list.map(parse_line)
@@ -18,8 +27,12 @@ pub fn pt_1(input: String) -> Int {
   |> int.sum
 }
 
-pub fn pt_2(_input: String) -> Int {
-  todo
+pub fn pt_2(input: String) -> Int {
+  string.split(input, on: "\n")
+  |> list.map(parse_line_pt2)
+  |> list.map(generate_hand)
+  |> list.map(score_game)
+  |> int.sum
 }
 
 fn parse_line(line: String) -> Game {
@@ -27,6 +40,11 @@ fn parse_line(line: String) -> Game {
   #(to_hand(a), to_hand(b))
 }
 
+fn parse_line_pt2(line: String) -> RiggedGame {
+  assert [a, b] = string.split(line, on: " ")
+  #(to_hand(a), to_outcome(b))
+}
+
 fn to_hand(raw: String) -> Hand {
   case raw {
     "A" -> Rock
@@ -38,6 +56,17 @@ fn to_hand(raw: String) -> Hand {
   }
 }
 
+// X means you need to lose,
+// Y means you need to end the round in a draw,
+// and Z means you need to win.
+fn to_outcome(raw: String) -> Outcome {
+  case raw {
+    "X" -> Lose
+    "Y" -> Draw
+    "Z" -> Win
+  }
+}
+
 fn score_game(game: Game) -> Int {
   let score = case game {
     // (them, me)
@@ -61,3 +90,16 @@ fn score_hand(hand: Hand) -> Int {
     Scissors -> 3
   }
 }
+
+/// Determine the hand to play give the opponent's hand and desired outcome
+fn generate_hand(game: RiggedGame) -> Game {
+  case game {
+    #(Rock, Lose) -> #(Rock, Scissors)
+    #(Rock, Win) -> #(Rock, Paper)
+    #(Paper, Lose) -> #(Paper, Rock)
+    #(Paper, Win) -> #(Paper, Scissors)
+    #(Scissors, Lose) -> #(Scissors, Paper)
+    #(Scissors, Win) -> #(Scissors, Rock)
+    #(_, Draw) -> #(game.0, game.0)
+  }
+}