Add 2016 solutions

2016/AoC2016.playground/Pages/Day 5.xcplaygroundpage/Contents.swift

@@ -0,0 +1,37 @@
+import CryptoKit
+import Foundation
+
+func char(_ string: String) -> (String, String)? {
+    let md5 = Insecure.MD5.hash(data: Data(string.utf8))
+    return md5.withUnsafeBytes { ptr in
+        guard ptr[0] == 0 && ptr[1] == 0 && ptr[2] & 0xf0 == 0 else { return nil }
+        return (
+            String(ptr[2] & 0x0f, radix: 16, uppercase: true),
+            String((ptr[3] >> 4) & 0x0f, radix: 16, uppercase: true)
+        )
+    }
+}
+
+var result1 = ""
+var result2 = "________"
+for i in 0... {
+    if let (first, second) = char("abbhdwsy\(i)") {
+        if result1.count < 8 {
+            result1 += first
+        }
+
+        if let i = Int(first), 0..<8 ~= i {
+            let index = result2.index(result2.startIndex, offsetBy: i)
+            if result2[index] == "_" {
+                result2.replaceSubrange(index...index, with: second)
+            }
+        }
+
+        if result1.count == 8 && !result2.contains("_") {
+            break
+        }
+    }
+}
+
+result1
+result2