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>
130 lines
2.0 KiB
Markdown
130 lines
2.0 KiB
Markdown
---
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id: 594810f028c0303b75339ad1
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title: Happy numbers
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challengeType: 5
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forumTopicId: 302280
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dashedName: happy-numbers
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---
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# --description--
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A [happy number](https://en.wikipedia.org/wiki/Happy_number) is defined by the following process:
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Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals `1` (where it will stay), or it loops endlessly in a cycle which does not include `1`. Those numbers for which this process ends in `1` are happy numbers, while those that do not end in `1` are unhappy numbers.
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# --instructions--
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Implement a function that returns true if the number is happy, or false if not.
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# --hints--
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`happy` should be a function.
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```js
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assert(typeof happy === 'function');
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```
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`happy(1)` should return a boolean.
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```js
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assert(typeof happy(1) === 'boolean');
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```
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`happy(1)` should return true.
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```js
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assert(happy(1));
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```
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`happy(2)` should return false.
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```js
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assert(!happy(2));
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```
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`happy(7)` should return true.
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```js
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assert(happy(7));
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```
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`happy(10)` should return true.
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```js
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assert(happy(10));
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```
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`happy(13)` should return true.
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```js
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assert(happy(13));
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```
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`happy(19)` should return true.
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```js
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assert(happy(19));
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```
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`happy(23)` should return true.
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```js
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assert(happy(23));
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```
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`happy(28)` should return true.
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```js
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assert(happy(28));
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```
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`happy(31)` should return true.
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```js
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assert(happy(31));
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```
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`happy(32)` should return true:.
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```js
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assert(happy(32));
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```
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`happy(33)` should return false.
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```js
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assert(!happy(33));
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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 happy(number) {
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}
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```
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# --solutions--
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```js
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function happy (number) {
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let m;
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let digit;
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const cycle = [];
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while (number !== 1 && cycle[number] !== true) {
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cycle[number] = true;
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m = 0;
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while (number > 0) {
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digit = number % 10;
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m += Math.pow(digit, 2);
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number = (number - digit) / 10;
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}
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number = m;
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}
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return (number === 1);
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}
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```
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