d11

day11/d11p1.swift

@@ -0,0 +1,62 @@
+import Foundation
+
+class Node : CustomStringConvertible {
+    var value: Int
+    var next: Node?
+    init(_ value: Int, next: Node? = nil) {
+        self.value = value
+        self.next = next
+    }
+    var description: String {
+        let nextStr = if let next { String(describing: next) } else { "nil" }
+        return "(\(value))->\(nextStr)"
+    }
+    func evolve() -> Int {
+        if value == 0 {
+            value = 1
+            return 1
+        }
+        // I don't have log10() unless I import Graphics, which is overkill...
+        let s = String(value)
+        if s.count.isMultiple(of: 2) {
+            let secondHalf = s.count/2 ..< s.count
+            let newNode = Node(Int(String(Array(s)[secondHalf]))!, next: next)
+            value = Int(String(Array(s)[0 ..< s.count/2]))!
+            next = newNode
+            return 2
+        }
+        value = value*2024
+        return 1
+    }
+}
+
+func readInput(_ filePath: String) throws -> Node {
+    let content = try String(contentsOfFile: filePath, encoding: .ascii)
+        .trimmingCharacters(in: .whitespacesAndNewlines)
+    let head: Node = Node(-1)
+    var current = head
+    content.split(separator: " ").forEach { i in
+        print(i)
+        let new = Node(Int(i)!)
+        current.next = new
+        current = new
+    }
+    return head.next!
+}
+
+func evolve(_ chain: Node) -> Int {
+    var next: Node? = chain
+    var count = 0
+    while let node = next {
+        next = node.next
+        count += node.evolve()
+    }
+    return count
+}
+
+let nums = try readInput(CommandLine.arguments[1])
+print(nums)
+for i in 1...25 {
+    let count = evolve(nums)
+    print("\(i): \(count)")  // - \(nums)")
+}