Coderbyte – Fibonacci Checker
Have the function FibonacciChecker(num) return the string yes if the number given is part of the Fibonacci sequence. This sequence is defined by: Fn = Fn-1 + Fn-2, which means to find Fn you add the previous two numbers up. The first two numbers are 0 and 1, then comes 1, 2, 3, 5 etc. If num is not in the Fibonacci sequence, return the string no.
function FibonacciChecker(num) {
// Initialize an array with the first value of the Fibonacci sequence
var prev = [0]
// Loop through each number in the sequence up to and including the input number
for (i = 1; i < num+1; i) {
// Calculate the next number in the sequence by adding the previous two
var check = i + prev[0]
// If the calculated number is equal to the input number, return "yes"
if (check === num) {
return 'yes'
}
// Add the current number to the beginning of the array to keep track of the previous two numbers
prev.unshift(i)
// Update the current number to be the next number in the sequence
i = check
}
// If the input number is not in the Fibonacci sequence, return "no"
return 'no'
}
// keep this function call here
console.log(FibonacciChecker(readline()));
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