remove debugging and failed trials

day20/d20p2.swift

@@ -3,72 +3,18 @@ import Foundation
 struct Coord : Hashable, CustomStringConvertible {
     let (x, y): (Int, Int)
     var description: String { return "(\(x), \(y))" }
+    func dist(to: Coord) -> Int { return abs(x - to.x) + abs(y - to.y) }
 }
 
-struct Queue<T> {
-    var arr: [T?]
-    var front: Int = 0
-    var back: Int = 0
-    init(size: Int) {
-        arr = Array(repeating: nil, count: size)
-    }
-    mutating func push(_ element: T) {
-        arr[back] = element
-        back += 1
-    }
-    mutating func pop() -> T? {
-        if front < back {
-            front += 1
-            return arr[front-1]
-        }
-        return nil
-    }
-}
-
-struct Maze : CustomStringConvertible {
+struct Maze {
     let (w, h): (Int, Int)
     let walls: Set<Coord>
     let (start, end): (Coord, Coord)
     let cheatMax: Int
-    var description: String {
-        var s = Array(repeating: Array(repeating: "  ", count: w), count: h)
-        walls.forEach { wall in
-            s[wall.y][wall.x] = "██"
-        }
-        path.forEach { cell, cost in
-            s[cell.y][cell.x] = String(format: "%2d", cost%100)
-        }
-        let hdr = "   " + (0..<w).map { " \($0 % 10)" }.joined() + "\n"
-        return hdr +
-            s.enumerated().map { i, c in
-                String(format: "%2d ", i) + c.joined() + "\n"
-            }.joined() + "\(start), \(end)"
-    }
-    var path: [Coord: Int] {
-        var cost: [Coord: Int] = [start: 0]
-        var cell = start
-        var prev = start
-        var currentCost = 0
-        while cell != end {
-            let next = neighbors(of: cell)
-                .filter(isPath)
-                .filter { $0 != prev }[0]
-            currentCost += 1
-            cost[next] = currentCost 
-            prev = cell
-            cell = next
-        }
-        return cost
-    }
 
     func valid(_ cell: Coord) -> Bool {
-        return cell.x >= 0 && cell.x < w && cell.y >= 0 && cell.y < h
-    }
-    func isPath(_ cell: Coord) -> Bool {
-        return !walls.contains(cell)
-    }
-    func isWall(_ cell: Coord) -> Bool {
-        return walls.contains(cell)
+        return cell.x >= 0 && cell.x < w && cell.y >= 0 && cell.y < h &&
+            !walls.contains(cell)
     }
 
     func neighbors(of cell: Coord) -> [Coord] {
@@ -76,49 +22,20 @@ struct Maze : CustomStringConvertible {
             .map { Coord(x: cell.x + $0, y: cell.y + $1) }.filter(valid)
     }
 
-    /*
-    func cheats(from entryCell: Coord) -> [Coord: Int] {
-        var q = Queue<(Coord, Int)>(size: cheatMax*cheatMax*2*2)
-        q.push((entryCell, 0))
-        var seen: Set<Coord> = [entryCell]
-        var jumps: [Coord: Int] = [:]
-        while let (cell, dist) = q.pop() {
-            neighbors(of: cell).filter { !seen.contains($0) }.forEach { nb in
-                seen.insert(nb)
-                if isPath(nb) {
-                    if dist + 1 <= cheatMax {
-                        //print("\(cell) -> \(nb) . \(dist + 1)")
-                        jumps[nb] = min(jumps[nb] ?? Int.max, dist + 1)
-                    }
-                } else if dist < cheatMax {
-                    //print("\(cell) -> \(nb) # \(dist + 1)")
-                    q.push((nb, dist + 1))
-               }
-            }
-        }
-        return jumps
-    }
-    */
     func cheats(from entry: Coord) -> [Coord: Int] {
-        let jumpList: [(Int, Int)] = (2...cheatMax).flatMap { dist in
-                (0..<dist).flatMap { d in
-                    let asdf: [(Int, Int)] = [
-                        (d, dist-d), (dist-d, -d), (-d, d-dist), (d-dist, d)
-                    ]
-                    return asdf
+        return Dictionary(uniqueKeysWithValues: (2...cheatMax)
+            .flatMap { dist -> [(Int, Int)] in
+                (0..<dist).flatMap { d -> [(Int, Int)] in
+                    [(d, dist-d), (dist-d, -d), (-d, d-dist), (d-dist, d)]
                 }
             }
-        let jumpCoords: [Coord] = jumpList
-            .map { dx, dy in Coord(x: entry.x + dx, y: entry.y + dy) }
-            .filter(valid).filter(isPath)
-        var res: [Coord: Int] = [:]
-        jumpCoords.forEach { end in
-            res[end] = abs(end.x - entry.x) + abs(end.y - entry.y)
-        }
-        return res
+            .map { dx, dy -> Coord in Coord(x: entry.x + dx, y: entry.y + dy) }
+            .filter(valid)
+            .map { end -> (Coord, Int) in (end, entry.dist(to: end)) }
+        )
     }
 
-    func cheats() -> [(Coord, Coord, Int, Int)] {
+    func cheats() -> [Int] {
         var cost: [Coord: Int] = [start: 0]
         var jumps: [(Coord, Coord, Int)] = []
         var cell = start
@@ -131,16 +48,13 @@ struct Maze : CustomStringConvertible {
                 .map { dest, dist in (cell, dest, dist) }
             jumps.append(contentsOf: newCheats)
             // add cost to table
-            let next = neighbors(of: cell)
-                .filter(isPath)
-                .filter { $0 != prev }[0]
+            let next = neighbors(of: cell).filter { $0 != prev }[0]
             currentCost += 1
             cost[next] = currentCost 
             prev = cell
             cell = next
-            //print("looking at \(cell) \(cost[cell]!)")
         }
-        return jumps.map { from, to, dist in (from, to, cost[to]! - cost[from]! - dist, dist) }
+        return jumps.map { from, to, dist in cost[to]! - cost[from]! - dist }
     }
 }
 
@@ -168,19 +82,5 @@ func readInput(_ filePath: String, _ cheatMax: Int) throws -> Maze {
 }
 
 let maze = try readInput(CommandLine.arguments[1], Int(CommandLine.arguments[2])!)
-print(maze)
-// print(maze.cheats(from: maze.start))
-let cheats = maze.cheats().filter { _, _, saving, _ in saving > 0 }
-let hist = cheats.reduce(into: [:]) { n, t in n[t.2, default: 0] += 1 }
-hist.keys.sorted().forEach { print("\(hist[$0]!) - \($0)") }
-print(cheats.filter { $0.2 >= 100 }.count)
-
-/*
-cheats
-    .filter { _, _, saving, _ in saving == 72 }
-    .forEach { from, to, save, dist in
-        print("\(path[from]!) -> \(path[to]!) = \(dist)(\(save))")
-    }
-print()
-*/
+print(maze.cheats().filter { $0 >= 100 }.count)