101 lines
2.6 KiB
Swift
101 lines
2.6 KiB
Swift
@main
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struct Day21: Puzzle {
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func run() {
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part1()
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part2()
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}
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let player1 = Player(position: 6)
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let player2 = Player(position: 7)
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func part1() {
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var die = Die()
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var player1 = player1
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var player2 = player2
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while true {
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if player1.move(die.roll3()) >= 1000 {
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print("Part 1: Player 1 won. ", die.rolls * player2.score)
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break
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}
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if player2.move(die.roll3()) >= 1000 {
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print("Part 1: Player 2 won. ", die.rolls * player1.score)
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break
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}
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}
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}
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func part2() {
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var universes: [Universe: Int] = [Universe(player1: player1, player2: player2): 1]
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var player1Wins = 0
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var player2Wins = 0
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while !universes.isEmpty {
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var newUniverses: [Universe: Int] = [:]
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for (universe, universeCount) in universes {
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for (offset, player1RollCount) in rollCounts.enumerated() {
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var u = universe
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if u.player1.move(offset + minRoll) >= quantumMax {
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player1Wins += universeCount * player1RollCount
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continue
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}
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for (offset, player2RollCount) in rollCounts.enumerated() {
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var u2 = u
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if u2.player2.move(offset + minRoll) >= quantumMax {
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player2Wins += universeCount * player1RollCount * player2RollCount
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continue
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}
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newUniverses[u2, default: 0] += universeCount * player1RollCount * player2RollCount
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}
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}
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}
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universes = newUniverses
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}
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print("Part 2: ", max(player1Wins, player2Wins))
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}
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let quantumMax = 21
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let minRoll = 3
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// 3 4 5 6 7 8 9
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let rollCounts = [1, 3, 6, 7, 6, 3, 1]
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struct Universe: Hashable {
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var player1: Player
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var player2: Player
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}
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struct Player: Hashable {
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var position: Int
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var score: Int = 0
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mutating func move(_ roll: Int) -> Int {
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position = 1 + (position + roll - 1) % 10
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score += position
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return score
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}
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}
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struct Die {
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var rolls = 0
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var nextRoll = 1
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mutating func roll() -> Int {
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defer {
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rolls += 1
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nextRoll += 1
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}
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return nextRoll
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}
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mutating func roll3() -> Int {
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roll() + roll() + roll()
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}
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}
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}
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