90 lines
1.6 KiB
Markdown
90 lines
1.6 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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---
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## Description
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<section id='description'>
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<p>Write a function to return the factorial of a number.</p>
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<p>Factorial of a number is given by : </p>
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n! = n * (n-1) * (n-2) * ..... * 1
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<p>
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For example :
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3! = 3*2*1 = 6
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4! = 4*3*2*1 = 24
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</p>
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<p>Note :
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0! = 1
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</p>
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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> is a function.
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testString: 'assert(typeof factorial === ''function'', ''<code>factorial</code> is a function.'');'
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- text: <code>factorial(2)</code> should return a number.
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testString: 'assert(typeof factorial(2) === ''number'', ''<code>factorial(2)</code> should return a number.'');'
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- text: <code>factorial(3)</code> should return 6.")
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testString: 'assert.equal(factorial(3),results[0],"<code>factorial(3)</code> should return 6.");'
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- text: <code>factorial(3)</code> should return 120.")
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testString: 'assert.equal(factorial(5),results[1],"<code>factorial(3)</code> should return 120.");'
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- text: '<code>factorial(3)</code> should return 3,628,800.")'
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testString: 'assert.equal(factorial(10),results[2],"<code>factorial(3)</code> should return 3,628,800.");'
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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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// Good luck!
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}
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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console.info('after the test');
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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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