81 lines
1.6 KiB
Markdown
81 lines
1.6 KiB
Markdown
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---
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id: 5900f4531000cf542c50ff65
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challengeType: 5
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title: 'Problem 230: Fibonacci Words'
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---
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## Description
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<section id='description'>
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For any two strings of digits, A and B, we define FA,B to be the sequence (A,B,AB,BAB,ABBAB,...) in which each term is the concatenation of the previous two.
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Further, we define DA,B(n) to be the nth digit in the first term of FA,B that contains at least n digits.
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Example:
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Let A=1415926535, B=8979323846. We wish to find DA,B(35), say.
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The first few terms of FA,B are:
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1415926535
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8979323846
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14159265358979323846
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897932384614159265358979323846
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14159265358979323846897932384614159265358979323846
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Then DA,B(35) is the 35th digit in the fifth term, which is 9.
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Now we use for A the first 100 digits of π behind the decimal point:
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14159265358979323846264338327950288419716939937510
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58209749445923078164062862089986280348253421170679
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and for B the next hundred digits:
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82148086513282306647093844609550582231725359408128
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48111745028410270193852110555964462294895493038196 .
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Find ∑n = 0,1,...,17 10n× DA,B((127+19n)×7n) .
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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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- text: <code>euler230()</code> should return 850481152593119200.
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testString: 'assert.strictEqual(euler230(), 850481152593119200, "<code>euler230()</code> should return 850481152593119200.");'
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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 euler230() {
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// Good luck!
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return true;
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}
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euler230();
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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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