From 7f201a614b95f52b0800f70a615d580b5ce4c7c4 Mon Sep 17 00:00:00 2001
From: Max Nuding <max.nuding@icloud.com>
Date: Sun, 12 Dec 2021 10:43:05 +0100
Subject: [PATCH] 12b

---
 Sources/12/12.swift                        | 70 ++++++++++++++++++----
 Sources/Runner/Resources/input/12_test.txt | 17 +++---
 2 files changed, 64 insertions(+), 23 deletions(-)

diff --git a/Sources/12/12.swift b/Sources/12/12.swift
index 668e9b5..5bf2e85 100644
--- a/Sources/12/12.swift
+++ b/Sources/12/12.swift
@@ -23,33 +23,42 @@ class Cave: Hashable, CustomStringConvertible, CustomDebugStringConvertible {
     var connectedCaves = [Cave]()
     var isBigCave: Bool
     var isEnd: Bool
+    var isStart: Bool
     
     required init(name: String) {
         self.name = name
         self.isBigCave = name.first!.isUppercase
         self.isEnd = name == "end"
+        self.isStart = name == "start"
     }
 }
 
-class Path: Hashable, CustomStringConvertible {
-    static func == (lhs: Path, rhs: Path) -> Bool {
-        lhs.parts == rhs.parts
+struct Path: Hashable, CustomStringConvertible {
+    var parts: [Cave]
+    var visitedSmallCaveTwice = false
+    var description: String
+    
+    func contains(cave: Cave) -> Bool { parts.contains(cave) }
+    
+    func appending(cave: Cave) -> Path {
+        var newParts = parts
+        newParts.append(cave)
+        return Path(
+            parts: newParts,
+            visitedSmallCaveTwice: visitedSmallCaveTwice || !cave.isBigCave && contains(cave: cave))
     }
     
+    static func == (lhs: Path, rhs: Path) -> Bool { lhs.description == rhs.description }
+    
     func hash(into hasher: inout Hasher) {
-        hasher.combine(parts)
+        hasher.combine(description)
     }
     
-    var parts: [Cave]
-    private var partsSet: Set<Cave>
-    var description: String { parts.map {$0.description}.joined(separator: "->") }
-    
-    required init(parts: [Cave]) {
+    init(parts: [Cave], visitedSmallCaveTwice: Bool = false) {
         self.parts = parts
-        partsSet = Set(parts)
+        self.visitedSmallCaveTwice = visitedSmallCaveTwice
+        self.description = (visitedSmallCaveTwice ? "*" : "") + parts.map {$0.description}.joined(separator: "->")
     }
-    
-    func contains(cave: Cave) -> Bool { partsSet.contains(cave) }
 }
 
 class Day12: Runnable {
@@ -77,7 +86,12 @@ class Day12: Runnable {
                 caves[caveToName] = to
                 
             })
+        runA()
+        runB()
         
+    }
+    
+    func runA() {
         var queue = Deque<Path>(minimumCapacity: 10000)
         var visited = Set<Path>(minimumCapacity: 10000)
         var numFinished = 0
@@ -90,7 +104,6 @@ class Day12: Runnable {
             if visited.contains(cave!) {
                 continue
             }
-            //print("Current path: \(cave!)")
             visited.insert(cave!)
             
             cave!.parts.last!.connectedCaves
@@ -108,4 +121,35 @@ class Day12: Runnable {
         }
         print(numFinished)
     }
+    
+    func runB() {
+        var queue = Deque<Path>(minimumCapacity: 1000000)
+        var visited = Set<Path>(minimumCapacity: 1000000)
+        var numFinished = 0
+        
+        var cave: Path? = Path(parts: [caves["start"]!])
+        queue.append(cave!)
+        
+        while !queue.isEmpty {
+            cave = queue.popFirst()
+            if visited.contains(cave!) {
+                continue
+            }
+            visited.insert(cave!)
+            cave!.parts.last!.connectedCaves
+                .forEach {
+                    if $0.isStart || (cave!.visitedSmallCaveTwice && !$0.isBigCave && cave!.contains(cave: $0)) {
+                        return
+                    }
+                    if $0.isEnd {
+                        numFinished += 1
+                        return
+                    }
+                    var newParts = cave!.parts
+                    newParts.append($0)
+                    queue.append(cave!.appending(cave: $0))
+                }
+        }
+        print(numFinished)
+    }
 }
diff --git a/Sources/Runner/Resources/input/12_test.txt b/Sources/Runner/Resources/input/12_test.txt
index 62cc714..6fd8c41 100644
--- a/Sources/Runner/Resources/input/12_test.txt
+++ b/Sources/Runner/Resources/input/12_test.txt
@@ -1,10 +1,7 @@
-dc-end
-HN-start
-start-kj
-dc-start
-dc-HN
-LN-dc
-HN-end
-kj-sa
-kj-HN
-kj-dc
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end