d15

2024-12-15 15:17:48 -08:00
parent b8945e61a3
commit 779f21a289
6 changed files with 322 additions and 0 deletions
--- a/day15/d15p2.swift
+++ b/day15/d15p2.swift
@@ -0,0 +1,114 @@
+import Foundation
+
+enum Move: Character, CustomStringConvertible {
+    case n = "^"
+    case s = "v"
+    case e = ">"
+    case w = "<"
+    var description: String { return String(self.rawValue) }
+    var delta: (Int, Int) {
+        switch self {
+        case .n: return (0, -1)
+        case .s: return (0, 1)
+        case .e: return (1, 0)
+        case .w: return (-1, 0)
+        }
+    }
+}
+
+struct Item: Hashable, CustomStringConvertible {
+    let (x, y): (Int, Int)
+    var description: String { return "(\(x), \(y))" }
+    var gps: Int { return x + 100*y }
+    func move(_ m: Move) -> Item {
+        let (dx, dy) = m.delta
+        return Item(x: x + dx, y: y + dy)
+    }
+}
+
+struct Boxes {
+    var boxes: Set<Item> = []
+    func at(x: Int, y: Int) -> Item? {
+        if boxes.contains(Item(x: x, y: y)) { return Item(x: x, y: y) }
+        if boxes.contains(Item(x: x-1, y: y)) { return Item(x: x-1, y: y) }
+        return nil
+    }
+}
+
+struct Map: CustomStringConvertible {
+    let walls: Set<Item>
+    var boxes: Boxes = Boxes()
+    var bot = Item(x: 0, y: 0)
+    var (w, h): (Int, Int)
+    var description: String {
+        var s: [[String]] = Array(
+            repeating: Array(repeating: "  ", count: w*2), count: h
+        )
+        walls.forEach { w in s[w.y][w.x] = "██" }
+        boxes.boxes.forEach { b in s[b.y][b.x] = "🮇🮀"; s[b.y][b.x+1] = "🮀▌" }
+        s[bot.y][bot.x] = "🮕🮕"
+        return s.map { row in row.joined() }.joined(separator: "\n")
+    }
+    var gps: Int { return boxes.boxes.reduce(0) { s, box in s + box.gps } }
+
+    init(from s: ArraySlice<String.SubSequence>) {
+        var walls: Set<Item> = []
+        h = s.count
+        w = s[0].count
+        for (y, line) in s.enumerated() {
+            for (x0, char) in line.enumerated() {
+                let x = 2*x0
+                switch char {
+                case "#": walls.formUnion([Item(x: x, y: y), Item(x: x+1, y: y)])
+                case "O": boxes.boxes.insert(Item(x: x, y: y))
+                case "@": bot = Item(x: x, y: y)
+                default: ()
+                }
+            }
+        }
+        self.walls = walls
+    }
+
+    mutating func move(_ dir: Move) {
+        var pushes: Set<Item> = []
+        var nexts: Set<Item> = [bot.move(dir)]
+        while !nexts.isEmpty {
+            let next = nexts.removeFirst()
+            if let box = boxes.at(x: next.x, y: next.y) {
+                pushes.insert(box)
+                let movedBox = box.move(dir)
+                switch dir {
+                case Move.w: nexts.insert(movedBox)
+                case Move.e: nexts.insert(Item(x: movedBox.x+1, y: movedBox.y))
+                case Move.n, Move.s:
+                    nexts.insert(movedBox)
+                    nexts.insert(Item(x: movedBox.x+1, y: movedBox.y))
+                }
+                continue
+            }
+            if walls.contains(next) {
+                return
+            }
+        }
+        pushes.forEach { boxes.boxes.remove($0) }
+        pushes.forEach { boxes.boxes.insert($0.move(dir)) }
+        bot = bot.move(dir)
+    }
+}
+
+func readInput(_ filePath: String) throws -> (Map, [Move]) {
+    let content = try String(contentsOfFile: filePath, encoding: .ascii)
+    let lines = content.split(separator: "\n", omittingEmptySubsequences: false)
+    let blankIdx = lines.firstIndex(of: "")!
+    let moves = lines.suffix(from: blankIdx + 1).joined().map { Move(rawValue: $0)! }
+    return (Map(from: lines.prefix(blankIdx)), moves)
+}
+
+var (map, moves) = try readInput(CommandLine.arguments[1])
+print(map)
+print(moves)
+for move in moves {
+    map.move(move)
+}
+print(map)
+print(map.gps)