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Given a number, say prod (for product), we search two Fibonacci numbers F(n) and F(n+1) verifying F(n) * F(n+1) = prod.
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// Given a number, say prod (for product), we search two Fibonacci numbers F(n) and F(n+1) verifying F(n) * F(n+1) = prod | |
// My solution to the code wars challenge https://www.codewars.com/kata/5541f58a944b85ce6d00006a/train/javascript | |
// Not used for this, but here's some code to test if a number is in the Fibonacci sequence. | |
// const isPerfectSquare = num => { | |
// const sq = Math.sqrt(num); | |
// return sq * sq === num; | |
// } | |
// const isFib = num => { | |
// return isPerfectSquare(5 * num * num + 4) || isPerfectSquare(5 * num * num - 4); | |
// } | |
const phi = (Math.sqrt(5) + 1) / 2; | |
const getF = num => { | |
return Math.round(((Math.pow(phi, num)) - (-Math.pow(phi, -num))) / Math.sqrt(5)) | |
} | |
const testProduct = (f) => { | |
return getF(f) * getF(f + 1); | |
} | |
const productFib = prod => { | |
let fib = 0; | |
let candidate = 0; | |
let match = false; | |
while(candidate < prod + 1){ | |
fib += 1; | |
candidate = testProduct(fib); | |
if(candidate === prod){ | |
match = true; | |
break; | |
} | |
} | |
return [getF(fib), getF(fib + 1), match]; | |
} |
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