Add 2019 solutions

2019/AoC.playground/Pages/Day 16.xcplaygroundpage/Contents.swift

@@ -0,0 +1,50 @@
+
+func pattern(position: Int) -> DropFirstSequence<AnySequence<Int>>
+{
+    precondition(position >= 0)
+    let repeats = position + 1
+
+    let base = [0, 1, 0, -1]
+    return repeating(base.flatMap { Array(repeating: $0, count: repeats) }).dropFirst()
+}
+
+func repeating<T: Sequence>(_ sequence: T) -> AnySequence<T.Element>
+{
+    return AnySequence { () -> AnyIterator<T.Element> in
+        var it = sequence.makeIterator()
+        return AnyIterator { () -> T.Element? in
+            if let value = it.next() {
+                return value
+            }
+
+            it = sequence.makeIterator()
+            return it.next()
+        }
+    }
+}
+
+func phase(_ input: [Int]) -> [Int] {
+    var result: [Int] = []
+    return input.indices.map { i in
+        abs(zip(input, pattern(position: i)).reduce(0) { (accum: Int, value: (Int, Int)) -> Int in accum + value.0 * value.1 }) % 10
+        }
+    }
+
+let input = "59773419794631560412886746550049210714854107066028081032096591759575145680294995770741204955183395640103527371801225795364363411455113236683168088750631442993123053909358252440339859092431844641600092736006758954422097244486920945182483159023820538645717611051770509314159895220529097322723261391627686997403783043710213655074108451646685558064317469095295303320622883691266307865809481566214524686422834824930414730886697237161697731339757655485312568793531202988525963494119232351266908405705634244498096660057021101738706453735025060225814133166491989584616948876879383198021336484629381888934600383957019607807995278899293254143523702000576897358"
+
+var data: [Int] = input.map { $0.wholeNumberValue! }
+
+func readAt(_ index: Int) -> Int {
+    data[index ..< index + 8].reduce(0) { 10 * $0 + $1 }
+}
+
+readAt(readAt(0))
+
+
+//for i in 0..<100 {
+//    data = phase(data)
+//}
+//
+//print(data[0..<8])
+
+