ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
123 lines
2.4 KiB
Markdown
123 lines
2.4 KiB
Markdown
---
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id: 5a23c84252665b21eecc7e80
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title: Gray code
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challengeType: 5
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forumTopicId: 302276
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dashedName: gray-code
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---
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# --description--
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[Gray code](<https://en.wikipedia.org/wiki/Gray code>) is a form of binary encoding where transitions between consecutive numbers differ by only one bit.
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This is a useful encoding for reducing hardware data hazards with values that change rapidly and/or connect to slower hardware as inputs.
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It is also useful for generating inputs for [Karnaugh maps](<https://en.wikipedia.org/wiki/Karnaugh map>) in order from left to right or top to bottom.
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# --instructions--
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Create a function to encode a number to and decode a number from Gray code. The function should will have 2 parameters.
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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.
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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).
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There are many possible Gray codes. The following encodes what is called "binary reflected Gray code."
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Encoding (MSB is bit 0, b is binary, g is Gray code):
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<pre>if b[i-1] = 1
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g[i] = not b[i]
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else
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g[i] = b[i]
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</pre>
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Or:
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<pre>g = b xor (b logically right shifted 1 time)
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</pre>
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Decoding (MSB is bit 0, b is binary, g is Gray code):
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<pre>b[0] = g[0]<br>
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for other bits:
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b[i] = g[i] xor b[i-1]
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</pre>
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# --hints--
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`gray` should be a function.
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```js
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assert(typeof gray == 'function');
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```
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`gray(true,177)` should return a number.
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```js
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assert(typeof gray(true, 177) == 'number');
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```
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`gray(true,177)` should return `233`.
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```js
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assert.equal(gray(true, 177), 233);
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```
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`gray(true,425)` should return `381`.
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```js
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assert.equal(gray(true, 425), 381);
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```
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`gray(true,870)` should return `725`.
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```js
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assert.equal(gray(true, 870), 725);
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```
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`gray(false,233)` should return `177`.
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```js
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assert.equal(gray(false, 233), 177);
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```
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`gray(false,381)` should return `425`.
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```js
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assert.equal(gray(false, 381), 425);
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```
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`gray(false,725)` should return `870`.
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```js
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assert.equal(gray(false, 725), 870);
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```
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# --seed--
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## --seed-contents--
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```js
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function gray(enc, number) {
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}
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```
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# --solutions--
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```js
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function gray(enc, number){
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if(enc){
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return number ^ (number >> 1);
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}else{
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let n = number;
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while (number >>= 1) {
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n ^= number;
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}
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return n;
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}
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}
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```
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