113 lines
3.3 KiB
Swift
113 lines
3.3 KiB
Swift
import Foundation
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let input = """
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L5, R1, R4, L5, L4, R3, R1, L1, R4, R5, L1, L3, R4, L2, L4, R2, L4, L1, R3, R1, R1, L1, R1, L5, R5, R2, L5, R2, R1, L2, L4, L4, R191, R2, R5, R1, L1, L2, R5, L2, L3, R4, L1, L1, R1, R50, L1, R1, R76, R5, R4, R2, L5, L3, L5, R2, R1, L1, R2, L3, R4, R2, L1, L1, R4, L1, L1, R185, R1, L5, L4, L5, L3, R2, R3, R1, L5, R1, L3, L2, L2, R5, L1, L1, L3, R1, R4, L2, L1, L1, L3, L4, R5, L2, R3, R5, R1, L4, R5, L3, R3, R3, R1, R1, R5, R2, L2, R5, L5, L4, R4, R3, R5, R1, L3, R1, L2, L2, R3, R4, L1, R4, L1, R4, R3, L1, L4, L1, L5, L2, R2, L1, R1, L5, L3, R4, L1, R5, L5, L5, L1, L3, R1, R5, L2, L4, L5, L1, L1, L2, R5, R5, L4, R3, L2, L1, L3, L4, L5, L5, L2, R4, R3, L5, R4, R2, R1, L5
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"""
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enum Direction {
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case north
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case east
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case south
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case west
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func turnLeft() -> Direction {
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switch self {
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case .north: return .west
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case .east: return .north
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case .south: return .east
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case .west: return .south
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}
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}
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func turnRight() -> Direction {
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switch self {
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case .north: return .east
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case .east: return .south
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case .south: return .west
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case .west: return .north
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}
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}
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func move(units: Int) -> (north: Int, east: Int) {
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switch self {
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case .north: return (units, 0)
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case .east: return (0, units)
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case .south: return (-units, 0)
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case .west: return (0, -units)
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}
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}
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}
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struct Position: Hashable {
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var heading: Direction = .north
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var north: Int = 0
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var east: Int = 0
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mutating func move(left: Bool, units: Int) -> [Position] {
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heading = left ? heading.turnLeft() : heading.turnRight()
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let (north, east) = heading.move(units: 1)
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var result: [Position] = []
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for _ in 0..<units {
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self.north += north
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self.east += east
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result.append(self)
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}
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return result
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}
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static func == (lhs: Position, rhs: Position) -> Bool {
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lhs.north == rhs.north && lhs.east == rhs.east
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}
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func hash(into hasher: inout Hasher) {
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hasher.combine(north)
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hasher.combine(east)
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}
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var distance: Int {
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abs(north) + abs(east)
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}
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}
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let scanner = Scanner(string: input)
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extension Scanner {
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func scanDirection() -> Bool {
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if scanString("L") != nil { return true }
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if scanString("R") != nil { return false }
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fatalError("Invalid direction")
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}
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func scanMove() -> (Bool, Int) {
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let direction = scanDirection()
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guard let units = scanInt() else {
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fatalError("Invalid distance")
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}
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guard isAtEnd || scanString(",") != nil else {
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fatalError("Missing ,")
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}
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return (direction, units)
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}
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}
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var position = Position()
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var visited: Set<Position> = [position]
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var foundPart2 = false
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while !scanner.isAtEnd {
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let (direction, units) = scanner.scanMove()
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let path = position.move(left: direction, units: units)
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for position in path {
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if !foundPart2 && !visited.insert(position).inserted {
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print("Part 2: Visited again: \(position.distance): \(position.north)n, \(position.east)e")
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foundPart2 = true
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break
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}
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}
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}
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print("Part 1:", position.distance)
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