82 lines
1.4 KiB
Markdown
82 lines
1.4 KiB
Markdown
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---
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title: Factorial
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id: 597b2b2a2702b44414742771
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challengeType: 5
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forumTopicId: 302263
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---
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## Description
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<section id='description'>
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Write a function to return the factorial of a number.
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Factorial of a number is given by:
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<pre>
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<big>n! = n * (n-1) * (n-2) * ..... * 1</big>
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</pre>
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For example:
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<ul>
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<li><code>3! = 3 * 2 * 1 = 6</code></li>
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<li><code>4! = 4 * 3 * 2 * 1 = 24</code></li>
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</ul>
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<strong>Note:</strong> <code>0! = 1</code>
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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>factorial</code> should be a function.
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testString: assert(typeof factorial === 'function');
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- text: <code>factorial(2)</code> should return a number.
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testString: assert(typeof factorial(2) === 'number');
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- text: <code>factorial(3)</code> should return 6.
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testString: assert.equal(factorial(3), 6);
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- text: <code>factorial(5)</code> should return 120.
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testString: assert.equal(factorial(5), 120);
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- text: <code>factorial(10)</code> should return 3,628,800.
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testString: assert.equal(factorial(10), 3628800);
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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 factorial(n) {
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}
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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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function factorial(n) {
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let sum = 1;
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while (n > 1) {
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sum *= n;
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n--;
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}
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return sum;
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}
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```
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</section>
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