1 files changed, 215 insertions, 0 deletions
diff --git a/22/src/main.rs b/22/src/main.rs
new file mode 100644
index 0000000..9deabe0
--- /dev/null
+++ b/22/src/main.rs
@@ -0,0 +1,215 @@
+use advent_lib::prelude::*;
+
+//use std::collections::BTreeMap;
+use std::collections::BTreeSet;
+use std::convert::TryFrom;
+
+
+fn main() -> Result<()> {
+  let mut args = std::env::args();
+  if args.len() != 2 {
+    eprintln!("Usage: advent input");
+  }
+  let _ = args.next();
+  let filename = args.next().unwrap();
+
+  let input = advent_lib::read_lines_file(&filename)?;
+  let input = advent_lib::group_lines_by_blanks(input);
+
+  let mut decks: Vec<Vec<i64>> = Vec::new();
+
+  for player_input in &input {
+    let mut deck = Vec::new();
+
+    let mut card_iterator = player_input.iter();
+    let _ = card_iterator.next();
+    for line in card_iterator {
+      let card_id = line.parse::<i64>().unwrap();
+      deck.push(card_id);
+    }
+
+    decks.push(deck);
+  }
+
+  let (_winner, score) = run_game(&decks);
+
+  println!("{}", score);
+
+  let (_winner2, score2) = run_game2(&decks);
+
+  println!("{}", score2);
+
+  Ok(())
+}
+
+
+fn run_game(input_decks: &Vec<Vec<i64>>) -> (usize, i64) {
+  let mut decks: Vec<Vec<i64>> = Vec::new();
+  for input_deck in input_decks {
+    let mut deck = Vec::new();
+    for card in input_deck {
+      deck.push(*card);
+    }
+    decks.push(deck);
+  }
+
+  loop {
+    let mut is_game_over = false;
+    for deck in &decks {
+      if deck.len() == 0 {
+        is_game_over = true;
+        break;
+      }
+    }
+    if is_game_over {
+      break;
+    }
+
+    let round_winner;
+    if decks[0][0] > decks[1][0] {
+      round_winner = 0;
+    } else {
+      round_winner = 1;
+    }
+    let round_loser = 1 - round_winner;
+
+    let mut transferred_cards = Vec::new();
+    transferred_cards.push(decks[round_winner][0]);
+    transferred_cards.push(decks[round_loser][0]);
+
+    for i in 0 .. decks.len() {
+      let (_, rest_of_deck) = decks[i].split_at(1);
+      let new_deck;
+      if i == round_winner {
+        new_deck = [rest_of_deck, transferred_cards.as_slice()].concat();
+      } else {
+        new_deck = rest_of_deck.to_vec();
+      }
+      decks[i] = new_deck;
+    }
+  }
+
+  let mut winner = 0;
+  let mut score = 0;
+  for i in 0 .. decks.len() {
+    let deck = &decks[i];
+    if deck.len() > 0 {
+      winner = i;
+
+      for j in 0 .. deck.len() {
+        let j_from_bottom = i64::try_from(deck.len() - j).unwrap();
+        score += deck[j] * j_from_bottom;
+      }
+    }
+  }
+
+  (winner, score)
+}
+
+
+fn run_game2(input_decks: &Vec<Vec<i64>>) -> (usize, i64) {
+  let mut decks = copy_decks(input_decks);
+
+  let mut previous_configurations: BTreeSet<Vec<Vec<i64>>> = BTreeSet::new();
+
+  loop {
+    //println!("{:?}", decks);
+    let mut is_game_over = false;
+    for deck in &decks {
+      if deck.len() == 0 {
+        is_game_over = true;
+        break;
+      }
+    }
+    if is_game_over {
+      break;
+    }
+
+    if previous_configurations.contains(&decks) {
+      //println!("loop detected");
+      return (0, score_deck(&decks[0]));
+    }
+
+    previous_configurations.insert(copy_decks(&decks));
+
+    let round_winner;
+
+    if decks[0].len() >= usize::try_from(decks[0][0]).unwrap() + 1
+      && decks[1].len() >= usize::try_from(decks[1][0]).unwrap() + 1
+    {
+      let mut recursive_decks: Vec<Vec<i64>> = Vec::new();
+      for i in 0 .. decks.len() {
+        let mut recursive_deck = Vec::new();
+        let n_to_take = usize::try_from(decks[i][0]).unwrap();
+        for j in 1 .. n_to_take + 1 {
+          recursive_deck.push(decks[i][j]);
+        }
+        recursive_decks.push(recursive_deck);
+      }
+
+      let (recursive_winner, _) = run_game2(&recursive_decks);
+      round_winner = recursive_winner;
+      //println!("recursing {:?}", decks);
+    } else if decks[0][0] > decks[1][0] {
+      round_winner = 0;
+    } else {
+      round_winner = 1;
+    }
+
+    let round_loser = 1 - round_winner;
+
+    let mut transferred_cards = Vec::new();
+    transferred_cards.push(decks[round_winner][0]);
+    transferred_cards.push(decks[round_loser][0]);
+
+    for i in 0 .. decks.len() {
+      let (_, rest_of_deck) = decks[i].split_at(1);
+      let new_deck;
+      if i == round_winner {
+        new_deck = [rest_of_deck, transferred_cards.as_slice()].concat();
+      } else {
+        new_deck = rest_of_deck.to_vec();
+      }
+      decks[i] = new_deck;
+    }
+  }
+
+  let mut winner = 0;
+  let mut score = 0;
+  for i in 0 .. decks.len() {
+    if decks[i].len() > 0 {
+      winner = i;
+      score = score_deck(&decks[i]);
+    }
+  }
+
+  (winner, score)
+}
+
+
+fn copy_decks(input_decks: &Vec<Vec<i64>>) -> Vec<Vec<i64>> {
+  let mut decks: Vec<Vec<i64>> = Vec::new();
+
+  for input_deck in input_decks {
+    let mut deck = Vec::new();
+    for card in input_deck {
+      deck.push(*card);
+    }
+    decks.push(deck);
+  }
+
+  decks
+}
+
+
+fn score_deck(deck: &Vec<i64>) -> i64 {
+  let mut score = 0;
+
+  for i in 0 .. deck.len() {
+    let i_from_bottom = i64::try_from(deck.len() - i).unwrap();
+    score += deck[i] * i_from_bottom;
+  }
+
+  score
+}
+