Add 2019 solutions

2019/AoC.playground/Pages/Day 4.xcplaygroundpage/Contents.swift

@@ -0,0 +1,23 @@
+let min = 172930
+let max = 683082
+
+var count = 0
+outer: for i in min...max {
+    let s = String(i).compactMap { $0.wholeNumberValue }
+
+    var hasDouble = false
+
+    for (first, second) in zip(s, s.dropFirst()) {
+        if second < first {
+            continue outer
+        }
+
+        if first == second {
+            hasDouble = true
+        }
+    }
+
+    guard hasDouble else { continue }
+
+    count += 1
+}