56 lines
1.3 KiB
Markdown
56 lines
1.3 KiB
Markdown
---
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id: 5900f3b61000cf542c50fec9
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challengeType: 5
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title: 'Problem 74: Digit factorial chains'
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videoUrl: ''
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localeTitle: 问题74：数字因子链
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---
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## Description
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<section id="description">数字145是众所周知的，其数字的阶乘之和等于145：1！ + 4！ + 5！ = 1 + 24 + 120 = 145也许知名度较低的是169，因为它产生了最长的数字链，可以链接到169;事实证明，只存在三个这样的循环：169→363601→1454→169 871→45361→871 872→45362→872不难证明每个起始编号最终都会陷入循环。例如，69→363600→1454→169→363601（→1454）78→45360→871→45361（→871）540→145（→145）从69开始产生五个非重复项链，但最长起始数低于一百万的非重复链是60个项。起始数低于一百万的链中有多少个包含正好六十个非重复项？ </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>euler74()</code>应返回402。
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testString: 'assert.strictEqual(euler74(), 402, "<code>euler74()</code> should return 402.");'
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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 euler74() {
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// Good luck!
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return true;
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}
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euler74();
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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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