76 lines
1.1 KiB
Markdown
76 lines
1.1 KiB
Markdown
---
|
|
id: 597f24c1dda4e70f53c79c81
|
|
title: Fibonacci sequence
|
|
challengeType: 5
|
|
forumTopicId: 302268
|
|
dashedName: fibonacci-sequence
|
|
---
|
|
|
|
# --description--
|
|
|
|
Write a function to generate the <code>n<sup>th</sup></code> Fibonacci number.
|
|
|
|
The <code>n<sup>th</sup></code> Fibonacci number is given by:
|
|
|
|
<code>F<sub>n</sub> = F<sub>n-1</sub> + F<sub>n-2</sub></code>
|
|
|
|
The first two terms of the series are 0 and 1.
|
|
|
|
Hence, the series is: 0, 1, 1, 2, 3, 5, 8, 13...
|
|
|
|
# --hints--
|
|
|
|
`fibonacci` should be a function.
|
|
|
|
```js
|
|
assert(typeof fibonacci === 'function');
|
|
```
|
|
|
|
`fibonacci(2)` should return a number.
|
|
|
|
```js
|
|
assert(typeof fibonacci(2) == 'number');
|
|
```
|
|
|
|
`fibonacci(3)` should return 2.
|
|
|
|
```js
|
|
assert.equal(fibonacci(3), 2);
|
|
```
|
|
|
|
`fibonacci(5)` should return 5.
|
|
|
|
```js
|
|
assert.equal(fibonacci(5), 5);
|
|
```
|
|
|
|
`fibonacci(10)` should return 55.
|
|
|
|
```js
|
|
assert.equal(fibonacci(10), 55);
|
|
```
|
|
|
|
# --seed--
|
|
|
|
## --seed-contents--
|
|
|
|
```js
|
|
function fibonacci(n) {
|
|
|
|
}
|
|
```
|
|
|
|
# --solutions--
|
|
|
|
```js
|
|
function fibonacci(n) {
|
|
let a = 0, b = 1, t;
|
|
while (--n >= 0) {
|
|
t = a;
|
|
a = b;
|
|
b += t;
|
|
}
|
|
return a;
|
|
}
|
|
```
|