5kyu_ProductOfConsecutiveFibNumbers.js

// 5kyu - Product of Consecutive Fib Numbers

// The Fibonacci numbers are the numbers in the following integer sequence (Fn):

// 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, ...

// such as

// F(n) = F(n-1) + F(n-2) with F(0) = 0 and F(1) = 1.

// 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.

// Your function productFib takes an integer (prod) and returns an array:

// [F(n), F(n+1), true] or {F(n), F(n+1), 1} or (F(n), F(n+1), True)
// depending on the language if F(n) * F(n+1) = prod.

// If you don't find two consecutive F(m) verifying F(m) * F(m+1) = prodyou will return

// [F(m), F(m+1), false] or {F(n), F(n+1), 0} or (F(n), F(n+1), False)
// F(m) being the smallest one such as F(m) * F(m+1) > prod.

// Some Examples of Return:
// (depend on the language)

// productFib(714) # should return (21, 34, true), 
//                 # since F(8) = 21, F(9) = 34 and 714 = 21 * 34

// productFib(800) # should return (34, 55, false), 
//                 # since F(8) = 21, F(9) = 34, F(10) = 55 and 21 * 34 < 800 < 34 * 55
// -----
// productFib(714) # should return [21, 34, true], 
// productFib(800) # should return [34, 55, false], 
// -----
// productFib(714) # should return {21, 34, 1}, 
// productFib(800) # should return {34, 55, 0},        
// -----
// productFib(714) # should return {21, 34, true}, 
// productFib(800) # should return {34, 55, false}, 
// Note:
// You can see examples for your language in "Sample Tests".


function productFib(prod){
  let n = 0, np = 1;  
  while(n*np < prod) {
    np = n + np;
    n = np - n;
  }
  return [n, np, n*np === prod];
}