89 lines
3.0 KiB
Swift
89 lines
3.0 KiB
Swift
import Foundation
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struct Coord : Hashable, CustomStringConvertible {
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let (x, y): (Int, Int)
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var description: String { return "(\(x), \(y))" }
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}
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struct Maze : CustomStringConvertible {
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let (w, h): (Int, Int)
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let walls: Set<Coord>
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let (start, end): (Coord, Coord)
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var description: String {
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var s = Array(repeating: Array(repeating: " ", count: w), count: (h+1)/2)
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walls.forEach { wall in
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if wall.y.isMultiple(of: 2) {
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s[wall.y/2][wall.x] = (s[wall.y/2][wall.x] == " ") ? "▀" : "█"
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} else {
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s[wall.y/2][wall.x] = (s[wall.y/2][wall.x] == " ") ? "▄" : "█"
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}
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}
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return s.map { $0.joined() + "\n" }.joined() + "\(start), \(end)"
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}
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func valid(_ cell: Coord) -> Bool {
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return cell.x >= 0 && cell.x < w && cell.y >= 0 && cell.y < h &&
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!walls.contains(cell)
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}
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func neighbors(of cell: Coord) -> [Coord] {
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return [(-1, 0), (1, 0), (0, -1), (0, 1)]
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.map { dx, dy in Coord(x: cell.x + dx, y: cell.y + dy) }
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}
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func cheats(of cell: Coord) -> [Coord] {
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return [(-1, 0), (1, 0), (0, -1), (0, 1)]
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.map { dx, dy in Coord(x: cell.x + dx*2, y: cell.y + dy*2) }
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.filter(valid)
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}
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func cheats() -> [Int] {
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var cost: [Coord: Int] = [start: 0]
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var jumps: [(Coord, Coord)] = []
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var cell = start
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var prev = start
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var currentCost = 0
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while cell != end {
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// list potential cheats from current cell
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let newCheats = cheats(of: cell).filter { !cost.keys.contains($0) }
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jumps.append(contentsOf: newCheats.map { dest in (cell, dest)} )
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// add cost to table
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let next = neighbors(of: cell).filter(valid).filter { $0 != prev }[0]
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currentCost += 1
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cost[next] = currentCost
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prev = cell
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cell = next
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}
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return jumps.map { from, to in cost[to]! - cost[from]! - 2 }
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}
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}
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func readInput(_ filePath: String) throws -> Maze {
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let content = try String(contentsOfFile: filePath, encoding: .ascii)
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let lines = content.split(separator: "\n")
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let (w, h) = (lines[0].count, lines.count)
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var walls: Set<Coord> = []
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var (start, end) = (Coord(x: 0, y: 0), Coord(x: w-1, y: h-1))
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lines.enumerated().forEach { i, line in
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line.enumerated().forEach { j, cell in
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let coord = Coord(x: j, y: i)
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if cell == "#" {
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walls.insert(coord)
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} else if cell == "S" {
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start = coord
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} else if cell == "E" {
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end = coord
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}
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}
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}
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return Maze(w: w, h: h, walls: walls, start: start, end: end)
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}
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let maze = try readInput(CommandLine.arguments[1])
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print(maze)
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let cheats = maze.cheats()
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let hist = cheats.reduce(into: [:]) { counts, t in counts[t, default: 0] += 1 }
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hist.keys.sorted().forEach { print("\($0) -> \(hist[$0]!)") }
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print(cheats.filter { $0 >= 100 }.count)
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