mirror of
https://github.com/freeCodeCamp/freeCodeCamp.git
synced 2026-03-12 07:02:42 -04:00
123 lines
2.3 KiB
Markdown
123 lines
2.3 KiB
Markdown
---
|
||
id: 5a23c84252665b21eecc7e80
|
||
title: Gray code
|
||
challengeType: 1
|
||
forumTopicId: 302276
|
||
dashedName: 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.
|
||
|
||
第一个是布尔值。 该函数应编码为 true，解码为 false。 第二个参数是要编码/解码的数字。
|
||
|
||
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):
|
||
|
||
<pre>if b[i-1] = 1
|
||
g[i] = not b[i]
|
||
else
|
||
g[i] = b[i]
|
||
</pre>
|
||
|
||
Or:
|
||
|
||
<pre>g = b xor (b logically right shifted 1 time)
|
||
</pre>
|
||
|
||
Decoding (MSB is bit 0, b is binary, g is Gray code):
|
||
|
||
<pre>b[0] = g[0]<br>
|
||
for other bits:
|
||
b[i] = g[i] xor b[i-1]
|
||
</pre>
|
||
|
||
# --hints--
|
||
|
||
`gray` should be a function.
|
||
|
||
```js
|
||
assert(typeof gray == 'function');
|
||
```
|
||
|
||
`gray(true,177)` should return a number.
|
||
|
||
```js
|
||
assert(typeof gray(true, 177) == 'number');
|
||
```
|
||
|
||
`gray(true,177)` should return `233`.
|
||
|
||
```js
|
||
assert.equal(gray(true, 177), 233);
|
||
```
|
||
|
||
`gray(true,425)` should return `381`.
|
||
|
||
```js
|
||
assert.equal(gray(true, 425), 381);
|
||
```
|
||
|
||
`gray(true,870)` should return `725`.
|
||
|
||
```js
|
||
assert.equal(gray(true, 870), 725);
|
||
```
|
||
|
||
`gray(false,233)` should return `177`.
|
||
|
||
```js
|
||
assert.equal(gray(false, 233), 177);
|
||
```
|
||
|
||
`gray(false,381)` should return `425`.
|
||
|
||
```js
|
||
assert.equal(gray(false, 381), 425);
|
||
```
|
||
|
||
`gray(false,725)` should return `870`.
|
||
|
||
```js
|
||
assert.equal(gray(false, 725), 870);
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --seed-contents--
|
||
|
||
```js
|
||
function gray(enc, number) {
|
||
|
||
}
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```js
|
||
function gray(enc, number){
|
||
if(enc){
|
||
return number ^ (number >> 1);
|
||
}else{
|
||
let n = number;
|
||
|
||
while (number >>= 1) {
|
||
n ^= number;
|
||
}
|
||
return n;
|
||
}
|
||
}
|
||
```
|