Gray code
Karnaugh maps
Create functions to encode a number to and decode a number from Gray code.

Display the normal binary representations, Gray code representations, and decoded Gray code values for all 5-bit binary numbers (0-31 inclusive, leading 0's not necessary).

There are many possible Gray codes. The following encodes what is called "binary reflected Gray code."

Encoding (MSB is bit 0, b is binary, g is Gray code):

if b[i-1] = 1
   g[i] = not b[i]
else
   g[i] = b[i]
Or:

g = b xor (b logically right shifted 1 time)
Decoding (MSB is bit 0, b is binary, g is Gray code):

b[0] = g[0]

for other bits:
b[i] = g[i] xor b[i-1]
Reference
 Converting Between Gray and Binary Codes. It includes step-by-step animations.
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))")
}