Problem 44311. Number of Even Elements in Fibonacci Sequence

Created by Mehmet OZC

Solve Later

Find how many even Fibonacci numbers are available in the first d numbers.

Consider the following first 14 numbers

1 1 2 3 5 8 13 21 34 55 89 144 233 377 ...

4 of them are even.

Solve

Solution Stats

1891 Solutions
401 Solvers

Last Solution submitted on Nov 19, 2019

Last 200 Solutions

Problem Comments

2 Comments

2 Comments

Ren Liujie on 22 Dec 2017

Big number is a problem. Instead we can find the regular pattern in which those even and odd numbers appear. Then everything becomes simple and easy.

Lamour Haithem Firass on 21 Sep 2019

i have the program on my matlab it work normaly but cody does not accepet the code don't know why?????
function y = evenFibo(n)
y(1) = 1;y(2) = 1;
for i = 3:n
y(i) = y(i-1) + y(i-2);
end
e = y;
E = mod(e,2) == 0;
evennumbers = e(E);
y = length(evennumbers);
if n > 2
fprintf('The even Fibo number is: %d',y)
end
end

Solution Comments

Solution 1865516

3 Comments

3 Comments

SJ Won on 4 Jul 2019

What's wrong with this?? It's working in matlab for me .

Lamour Haithem Firass on 21 Sep 2019

me2

goc3 on 23 Oct 2019 at 23:28

The fibonacci() function is in a toolbox. Only functions in vanilla Matlab are recognized by Cody.

Solution 1319950

3 Comments

3 Comments

Leo Nunnink on 30 Oct 2017

My code works to d=50 and fails on the higher values in the test suite. I think it is a hardware-limited rounding error (?swamping) with very large numbers. When I test eps(fibonacci(100)) on my system, the answer is 6.5 ie my system can not accurately distinguish odd from even at that large a number.

James on 2 Nov 2017

Leo, your theory is correct: The numbers that you're calculating for d>50 are too large to be represented by a 32-bit digit, and won't be calculated correctly for mod(x,2). Think very carefully about the number pattern in the Fibonacci sequence, and see if a pattern emerges.

Mehdi BENSEDDIK on 4 Apr 2019

Indeed, My code works until the d = 50 because it's a large number, so our algorithm is correct we should not worry about it, I think we have succeed in this challenge.

Solution 1318351

1 Comment

1 Comment

David Verrelli on 3 Nov 2017

Not a true solution. Would fail if Test Suite were expanded.

Solution 1302521

1 Comment

1 Comment

David Verrelli on 3 Nov 2017

Not a general solution. Will fail if Test Suite expanded.

Problem Recent Solvers401

Problem Tags

Problem 44311. Number of Even Elements in Fibonacci Sequence

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers401

Suggested Problems

More from this Author57

Problem Tags

Problem 44311. Number of Even Elements in Fibonacci Sequence

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers401

Suggested Problems

More from this Author57

Problem Tags

Players