Merge pull request #317 from kriadmin/master

[FEATURE] Add two snippets fibsTillNum and fibonacciTillNum
This commit is contained in:
Angelos Chalaris
2017-12-23 12:19:41 +02:00
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2 changed files with 26 additions and 0 deletions

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### fibonacciCountUntilNum
Returns the number of fibonnacci numbers up to `num`(`0` and `num` inclusive).
Use a mathematical formula to calculate the number of fibonacci numbers until `num`.
```js
const fibonacciCountUntilNum = num =>
Math.ceil(Math.log(num * Math.sqrt(5) + 1/2) / Math.log((Math.sqrt(5)+1)/2));
// fibonacciCountUntilNum(10) -> 7
```

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### fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (`0` and `1`).
Use `Array.reduce()` to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
```js
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1/2) / Math.log((Math.sqrt(5)+1)/2));
return Array.from({ length: n}).reduce((acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i), []);
}
// fibonacciUntilNum(15) -> [0,1,1,2,3,5,8,13]
```