2022 Day 7

2022/day7.swift

@@ -0,0 +1,93 @@
+import Foundation
+
+class Directory {
+    var parent: Directory? = nil
+    var children: [String: Directory] = [:]
+    var size: Int = 0
+    
+    init(parent: Directory? = nil) {
+        self.parent = parent
+    }
+    
+    func child(_ name: String) -> Directory {
+        if let child = children[name] {
+            return child
+        }
+        
+        let new = Directory(parent: self)
+        children[name] = new
+        return new
+    }
+    
+    func totalSize() -> Int {
+        return size + children.values.reduce(0) { $0 + $1.totalSize() }
+    }
+    
+    func all(_ callback: (Directory) -> Void) {
+        callback(self)
+        for child in children.values {
+            child.all(callback)
+        }
+    }
+}
+
+let input = try String(contentsOf: URL(fileURLWithPath: "day7.input"))
+let scanner = Scanner(string: input)
+
+let root = Directory()
+var current: Directory? = nil
+
+while !scanner.isAtEnd {
+    guard scanner.scanString("$") != nil else {
+        fatalError("Expected $")
+    }
+    
+    if scanner.scanString("cd") != nil, let dir = scanner.scanUpToString("\n") {
+        switch dir {
+            case "/": 
+                current = root
+                
+            case "..":
+                current = current!.parent
+                
+            default:
+                current = current!.child(dir)
+        }
+    } else if scanner.scanString("ls") != nil {
+        while true {
+            if let size = scanner.scanInt() {
+                current!.size += size
+            } else if scanner.scanString("dir") != nil {
+                
+            } else {
+                break
+            }
+            _ = scanner.scanUpToString("\n");
+        }
+    }
+}
+
+var sum = 0
+root.all {
+    let size = $0.totalSize()
+    if size < 100000 {
+        sum += size
+    }
+}
+
+print("Part 1: Sum of size of all directories < 100000:", sum)
+
+let diskSize = 70000000
+let freeSpace = diskSize - root.totalSize()
+let requiredSize = 30000000
+let toFree = requiredSize - freeSpace
+
+var smallest = Int.max
+root.all {
+    let size = $0.totalSize()
+    if size >= toFree && size < smallest {
+        smallest = size
+    }
+}
+
+print("Part 2: Smallest folder to delete:", smallest)