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id	title	challengeType	forumTopicId	dashedName
5a23c84252665b21eecc7e80	Gray code	1	302276	gray-code

--description--

Gray code is a form of binary encoding where transitions between consecutive numbers differ by only one bit.

This is a useful encoding for reducing hardware data hazards with values that change rapidly and/or connect to slower hardware as inputs.

It is also useful for generating inputs for Karnaugh maps in order from left to right or top to bottom.

--instructions--

Create a function to encode a number to and decode a number from Gray code. The function should will have 2 parameters.

The first would be a boolean. The function should encode for true and decode for false. The second parameter would be the number to be encoded/decoded.

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]

--hints--

gray should be a function.

assert(typeof gray == 'function');

gray(true,177) should return a number.

assert(typeof gray(true, 177) == 'number');

gray(true,177) should return 233.

assert.equal(gray(true, 177), 233);

gray(true,425) should return 381.

assert.equal(gray(true, 425), 381);

gray(true,870) should return 725.

assert.equal(gray(true, 870), 725);

gray(false,233) should return 177.

assert.equal(gray(false, 233), 177);

gray(false,381) should return 425.

assert.equal(gray(false, 381), 425);

gray(false,725) should return 870.

assert.equal(gray(false, 725), 870);

--seed--

--seed-contents--

function gray(enc, number) {

}

--solutions--

function gray(enc, number){
  if(enc){
      return number ^ (number >> 1);
  }else{
      let n = number;

      while (number >>= 1) {
          n ^= number;
      }
      return n;
  }
}

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