65 lines
1.4 KiB
Markdown
65 lines
1.4 KiB
Markdown
---
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id: 5900f3a61000cf542c50feb9
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challengeType: 5
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title: 'Problem 58: Spiral primes'
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---
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## Description
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<section id='description'>
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Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed.
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37 36 35 34 33 32 31
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38 17 16 15 14 13 30
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39 18 5 4 3 12 29
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40 19 6 1 2 11 28
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41 20 7 8 9 10 27
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42 21 22 23 24 25 2643 44 45 46 47 48 49
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It is interesting to note that the odd squares lie along the bottom right diagonal, but what is more interesting is that 8 out of the 13 numbers lying along both diagonals are prime; that is, a ratio of 8/13 ≈ 62%.
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If one complete new layer is wrapped around the spiral above, a square spiral with side length 9 will be formed. If this process is continued, what is the side length of the square spiral for which the ratio of primes along both diagonals first falls below 10%?
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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>euler58()</code> should return 26241.
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testString: assert.strictEqual(euler58(), 26241, '<code>euler58()</code> should return 26241.');
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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 euler58() {
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// Good luck!
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return true;
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}
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euler58();
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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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