feature: add fast fibonacci algorithm (#1155)

This commit is contained in:
houcem testouri
2022-10-16 21:24:44 +01:00
committed by GitHub
parent 829d3fd807
commit e65211299b
2 changed files with 48 additions and 0 deletions

View File

@ -0,0 +1,25 @@
/**
* @function fastFibonacci
* @description fastFibonacci is same as fibonacci algorithm by calculating the sum of previous two fibonacci numbers but in O(log(n)).
* @param {Integer} N - The input integer
* @return {Integer} fibonacci of N.
* @see [Fast_Fibonacci_Numbers](https://www.geeksforgeeks.org/fast-doubling-method-to-find-the-nth-fibonacci-number/)
*/
// recursive function that returns (F(n), F(n-1))
const fib = (N) => {
if (N === 0) return [0, 1]
const [a, b] = fib(Math.trunc(N / 2))
const c = a * (b * 2 - a)
const d = a * a + b * b
return N % 2 ? [d, c + d] : [c, d]
}
const fastFibonacci = (N) => {
if (!Number.isInteger(N)) {
throw new TypeError('Input should be integer')
}
return fib(N)[0]
}
export { fastFibonacci }

View File

@ -0,0 +1,23 @@
import { fastFibonacci } from '../FastFibonacciNumber'
describe('Testing FibonacciNumber', () => {
const errorCases = ['0', '12', true]
test.each(errorCases)('throws an error if %p is invalid', (input) => {
expect(() => {
fastFibonacci(input)
}).toThrow()
})
const testCases = [
[0, 0],
[1, 1],
[10, 55],
[25, 75025],
[40, 102334155]
]
test.each(testCases)('if input is %i it returns %i', (input, expected) => {
expect(fastFibonacci(input)).toBe(expected)
})
})