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* fix: clean-up Project Euler 141-160 * fix: corrections from review Co-authored-by: Sem Bauke <46919888+Sembauke@users.noreply.github.com> * fix: corrections from review Co-authored-by: Tom <20648924+moT01@users.noreply.github.com> * fix: use different notation for consistency * Update curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-144-investigating-multiple-reflections-of-a-laser-beam.md Co-authored-by: gikf <60067306+gikf@users.noreply.github.com> Co-authored-by: Sem Bauke <46919888+Sembauke@users.noreply.github.com> Co-authored-by: Tom <20648924+moT01@users.noreply.github.com>
43 lines
977 B
Markdown
43 lines
977 B
Markdown
---
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id: 5900f3fd1000cf542c50ff10
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title: 'Problem 145: How many reversible numbers are there below one-billion?'
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challengeType: 5
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forumTopicId: 301774
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dashedName: problem-145-how-many-reversible-numbers-are-there-below-one-billion
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---
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# --description--
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Some positive integers $n$ have the property that the sum [ $n + reverse(n)$ ] consists entirely of odd (decimal) digits. For instance, $36 + 63 = 99$ and $409 + 904 = 1313$. We will call such numbers reversible; so 36, 63, 409, and 904 are reversible. Leading zeroes are not allowed in either $n$ or $reverse(n)$.
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There are 120 reversible numbers below one-thousand.
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How many reversible numbers are there below one-billion (${10}^9$)?
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# --hints--
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`reversibleNumbers()` should return `608720`.
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```js
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assert.strictEqual(reversibleNumbers(), 608720);
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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 reversibleNumbers() {
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return true;
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}
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reversibleNumbers();
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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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