f1c9b08cf3
This includes certificates (where it does nothing), but does not include any translations.
74 lines
1.4 KiB
Markdown
74 lines
1.4 KiB
Markdown
---
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id: 5900f3c81000cf542c50fedb
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challengeType: 5
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isHidden: false
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title: 'Problem 92: Square digit chains'
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forumTopicId: 302209
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---
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## Description
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<section id='description'>
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A number chain is created by continuously adding the square of the digits in a number to form a new number until it has been seen before.
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For example,
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<div style='margin-left: 4em;'>
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44 → 32 → 13 → 10 → <strong>1</strong> → <strong>1</strong><br>
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85 → <strong>89</strong> → 145 → 42 → 20 → 4 → 16 → 37 → 58 → <strong>89</strong>
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</div>
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Therefore any chain that arrives at 1 or 89 will become stuck in an endless loop. What is most amazing is that EVERY starting number will eventually arrive at 1 or 89.
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How many starting numbers below ten million will arrive at 89?
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>squareDigitChains()</code> should return a number.
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testString: assert(typeof squareDigitChains() === 'number');
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- text: <code>squareDigitChains()</code> should return 8581146.
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testString: assert.strictEqual(squareDigitChains(), 8581146);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function squareDigitChains() {
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// Good luck!
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return true;
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}
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squareDigitChains();
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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