56 lines
1.1 KiB
Markdown
56 lines
1.1 KiB
Markdown
---
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id: 5900f3c81000cf542c50fedb
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title: 'Problem 92: Square digit chains'
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challengeType: 5
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forumTopicId: 302209
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dashedName: problem-92-square-digit-chains
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---
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# --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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# --hints--
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`squareDigitChains()` should return a number.
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```js
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assert(typeof squareDigitChains() === 'number');
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```
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`squareDigitChains()` should return 8581146.
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```js
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assert.strictEqual(squareDigitChains(), 8581146);
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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 squareDigitChains() {
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return true;
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}
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squareDigitChains();
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```
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# --solutions--
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```js
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// solution required
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```
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