diff --git a/Package.swift b/Package.swift
index 1ac491e..02c3197 100644
--- a/Package.swift
+++ b/Package.swift
@@ -20,7 +20,8 @@ let package = Package(
             .executable(name: "08", targets: ["08"]),
             .executable(name: "09", targets: ["09"]),
             .executable(name: "10", targets: ["10"]),
-            .executable(name: "11", targets: ["11"])
+            .executable(name: "11", targets: ["11"]),
+            .executable(name: "12", targets: ["12"])
         ],
     dependencies: [
         // Dependencies declare other packages that this package depends on.
@@ -92,9 +93,13 @@ let package = Package(
         ),
         .executableTarget(
             name: "11",
+            dependencies: [ .targetItem(name: "Runner", condition: nil) ]
+        ),
+        .executableTarget(
+            name: "12",
             dependencies: [
                 .targetItem(name: "Runner", condition: nil),
-                //.product(name: "Collections", package: "swift-collections"),
+                .product(name: "Collections", package: "swift-collections")
             ]
         )
     ]
diff --git a/Sources/11/11.swift b/Sources/11/11.swift
index d665757..4ebc124 100644
--- a/Sources/11/11.swift
+++ b/Sources/11/11.swift
@@ -49,14 +49,14 @@ class Day11: Runnable {
             .map { Array($0) }
             .map { ar in ar.map {c in Int(c.description)!} }
          
-        for _ in 0..<100 {
+        var step = 0
+        while(flashed.count < numRows * numCols) {
             flashed = Set<Coord>()
             for row in octopuses.indices {
                 for col in octopuses[row].indices {
                     octopuses[row][col] += 1
                 }
             }
-            
             for row in octopuses.indices {
                 for col in octopuses[row].indices {
                     let coord = Coord(row: row, col: col)
@@ -66,8 +66,12 @@ class Day11: Runnable {
             for flash in flashed {
                 octopuses[flash] = 0
             }
+            step += 1
+            if step == 100 {
+                print(numFlashes)
+            }
         }
-        print(numFlashes)
+        print("All flashing at step: \(step)")
     }
     
     func checkAndFlash(at coord: Coord) {
diff --git a/Sources/12/12.swift b/Sources/12/12.swift
new file mode 100644
index 0000000..668e9b5
--- /dev/null
+++ b/Sources/12/12.swift
@@ -0,0 +1,111 @@
+//
+//  File.swift
+//
+//
+//  Created by Max Nuding on 12.12.21.
+//
+
+import Foundation
+import Runner
+import Collections
+
+class Cave: Hashable, CustomStringConvertible, CustomDebugStringConvertible {
+    static func == (lhs: Cave, rhs: Cave) -> Bool { lhs.name == rhs.name }
+    
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(name)
+    }
+    
+    var description: String { name }
+    var debugDescription: String { name }
+    
+    let name: String
+    var connectedCaves = [Cave]()
+    var isBigCave: Bool
+    var isEnd: Bool
+    
+    required init(name: String) {
+        self.name = name
+        self.isBigCave = name.first!.isUppercase
+        self.isEnd = name == "end"
+    }
+}
+
+class Path: Hashable, CustomStringConvertible {
+    static func == (lhs: Path, rhs: Path) -> Bool {
+        lhs.parts == rhs.parts
+    }
+    
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(parts)
+    }
+    
+    var parts: [Cave]
+    private var partsSet: Set<Cave>
+    var description: String { parts.map {$0.description}.joined(separator: "->") }
+    
+    required init(parts: [Cave]) {
+        self.parts = parts
+        partsSet = Set(parts)
+    }
+    
+    func contains(cave: Cave) -> Bool { partsSet.contains(cave) }
+}
+
+class Day12: Runnable {
+    let inputPath: String
+    var caves = [String:Cave]()
+    
+    required init(inputPath: String) {
+        self.inputPath = inputPath
+    }
+    
+    public func run() {
+        let input = try! String(contentsOfFile: inputPath)
+        caves = input
+            .trimmingCharacters(in: .newlines)
+            .components(separatedBy: .newlines)
+            .reduce(into: [String:Cave](), { caves, line in
+                let caveConnection = line.components(separatedBy: "-")
+                let caveFromName = caveConnection.first!
+                let caveToName = caveConnection.last!
+                let from = caves[caveFromName] ?? Cave(name: caveFromName)
+                let to = caves[caveToName] ?? Cave(name: caveToName)
+                from.connectedCaves.append(to)
+                to.connectedCaves.append(from)
+                caves[caveFromName] = from
+                caves[caveToName] = to
+                
+            })
+        
+        var queue = Deque<Path>(minimumCapacity: 10000)
+        var visited = Set<Path>(minimumCapacity: 10000)
+        var numFinished = 0
+        
+        var cave: Path? = Path(parts: [caves["start"]!])
+        queue.append(cave!)
+        
+        while !queue.isEmpty {
+            cave = queue.popFirst()
+            if visited.contains(cave!) {
+                continue
+            }
+            //print("Current path: \(cave!)")
+            visited.insert(cave!)
+            
+            cave!.parts.last!.connectedCaves
+                .filter { $0.isBigCave || !cave!.contains(cave: $0) }
+                .forEach {
+                    if $0.isEnd {
+                        numFinished += 1
+                        //print("Finished: \(cave!.parts)->end")
+                        return
+                    }
+                    var newParts = cave!.parts
+                    newParts.append($0)
+                    queue.append(Path(parts: newParts))
+                }
+        }
+        print(numFinished)
+    }
+}
diff --git a/Sources/12/main.swift b/Sources/12/main.swift
new file mode 100644
index 0000000..21793cd
--- /dev/null
+++ b/Sources/12/main.swift
@@ -0,0 +1,12 @@
+//
+//  File.swift
+//  
+//
+//  Created by Max Nuding on 05.12.21.
+//
+
+import Foundation
+import Runner
+
+//Runner(target: Day12.self, day: "12", isTest: true).run()
+Runner(target: Day12.self, day: "12", isTest: false).run()
diff --git a/Sources/Runner/Resources/input/12.txt b/Sources/Runner/Resources/input/12.txt
new file mode 100644
index 0000000..607ff61
--- /dev/null
+++ b/Sources/Runner/Resources/input/12.txt
@@ -0,0 +1,25 @@
+start-kc
+pd-NV
+start-zw
+UI-pd
+HK-end
+UI-kc
+pd-ih
+ih-end
+start-UI
+kc-zw
+end-ks
+MF-mq
+HK-zw
+LF-ks
+HK-kc
+ih-HK
+kc-pd
+ks-pd
+MF-pd
+UI-zw
+ih-NV
+ks-HK
+MF-kc
+zw-NV
+NV-ks
diff --git a/Sources/Runner/Resources/input/12_test.txt b/Sources/Runner/Resources/input/12_test.txt
new file mode 100644
index 0000000..62cc714
--- /dev/null
+++ b/Sources/Runner/Resources/input/12_test.txt
@@ -0,0 +1,10 @@
+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc