31 lines
721 B
Markdown
31 lines
721 B
Markdown
importance: 4
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---
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# Calculate factorial
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The [factorial](https://en.wikipedia.org/wiki/Factorial) of a natural number is a number multiplied by `"number minus one"`, then by `"number minus two"`, and so on till `1`. The factorial of `n` is denoted as `n!`
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We can write a definition of factorial like this:
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```js
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n! = n * (n - 1) * (n - 2) * ...*1
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```
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Values of factorials for different `n`:
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```js
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1! = 1
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2! = 2 * 1 = 2
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3! = 3 * 2 * 1 = 6
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4! = 4 * 3 * 2 * 1 = 24
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5! = 5 * 4 * 3 * 2 * 1 = 120
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```
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The task is to write a function `factorial(n)` that calculates `n!` using recursive calls.
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```js
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alert( factorial(5) ); // 120
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```
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P.S. Hint: `n!` can be written as `n * (n-1)!` For instance: `3! = 3*2! = 3*2*1! = 6`
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