Family Day update

Task/Gray-code/Swift/gray-code.swift

@@ -0,0 +1,22 @@
+func grayEncode(_ i: Int) -> Int {
+  return (i >> 1) ^ i
+}
+
+func grayDecode(_ i: Int) -> Int {
+  switch i {
+  case 0:
+    return 0
+  case _:
+    return i ^ grayDecode(i >> 1)
+  }
+}
+
+for i in 0..<32 {
+  let iStr = String(i, radix: 2)
+  let encode = grayEncode(i)
+  let encodeStr = String(encode, radix: 2)
+  let decode = grayDecode(encode)
+  let decodeStr = String(decode, radix: 2)
+
+  print("\(i) (\(iStr)) => \(encode) (\(encodeStr)) => \(decode) (\(decodeStr))")
+}