Move to subdirectory

2020/day23/main.swift

@@ -0,0 +1,112 @@
+var nodesByValue: [Node?] = Array(repeating: nil, count: 1000001)
+
+final class Node {
+    var next: Node!
+    var value: Int
+
+    init(value: Int, next: Node? = nil) {
+        self.value = value
+        self.next = next
+    }
+
+    static func make(_ values: [Int]) -> Node {
+        precondition(!values.isEmpty)
+
+        let first = Node(value: values[0])
+        nodesByValue[values[0]] = first
+        first.next = first
+
+        var current = first
+        for value in values.dropFirst() {
+            let new = Node(value: value, next: first)
+            nodesByValue[value] = new
+            current.next = new
+            current = new
+        }
+
+        for value in 10...1000000 {
+            let new = Node(value: value, next: first)
+            nodesByValue[value] = new
+            current.next = new
+            current = new
+        }
+
+        return first
+    }
+
+    func find(value: Int) -> Node? {
+        return nodesByValue[value]
+    }
+}
+
+let input = [9, 5, 2, 3, 1, 6, 4, 8, 7]
+let max = 1000000
+//let max = input.max()!
+
+let node = Node.make(input)
+var selected = node
+
+func rangeContains(value: Int, start: Node,  end: Node) -> Bool {
+    var current = start
+    while current !== end.next {
+        if current.value == value {
+            return true
+        }
+        current = current.next
+    }
+    return false
+}
+
+func round() {
+    let firstPick: Node = selected.next
+    let lastPick: Node = firstPick.next.next
+
+    selected.next = lastPick.next
+
+    var destination = selected.value
+    repeat {
+        destination -= 1
+        if destination < 1 {
+            destination = max
+        }
+    } while rangeContains(value: destination, start: firstPick, end: lastPick)
+
+    let toInsert = lastPick.next.find(value: destination)!
+    lastPick.next = toInsert.next
+    toInsert.next = firstPick
+
+    selected = selected.next
+}
+
+func printStack() {
+    var current = node
+    repeat {
+        print(current === selected ? "(\(current.value))" : "\(current.value)", terminator: " ")
+        current = current.next
+    } while current !== node
+    print()
+}
+
+func showSolution() {
+    let start = node.find(value: 1)!
+    var one: Node = start.next
+    while one !== start {
+        print(one.value, terminator: "")
+        one = one.next
+    }
+    print()
+
+}
+
+for i in 0..<10_000_000 {
+//    print("\(i + 1)) ", terminator: "")
+//    printStack()
+    round()
+}
+
+//print("Final: ", terminator: "")
+//printStack()
+//showSolution()
+
+let one = node.find(value: 1)!
+print(one.next.value * one.next.next.value)