Problem 44311. Number of Even Elements in Fibonacci Sequence

Created by Mehmet OZC

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3198 Solutions
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Last Solution submitted on Jan 24, 2021

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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

Highphi on 26 Jul 2020

Gorgeously simple once you figure it out
hint: copy and paste the first few test suites into your MATLAB console and try plotting it with ':o'

Jiseon Shin on 28 Oct 2020

My solution is working in my local computer but is not consistent with Test Suites starting from d = 100. I don't still get the answer.

Solution Comments

Solution 3658988

1 Comment

1 Comment

Mengyuan Zhang on 14 Nov 2020

One liner solution:
function y = evenFibo(d)
y = floor(d/3);
end

Solution 3197881

1 Comment

1 Comment

Asrorkhuja Ortikov on 13 Oct 2020

it is working in my Matlab

Solution 2714223

1 Comment

1 Comment

Mohamed AIDAHI on 20 Jul 2020

i'm pretty confident of my code but it doesn't work for d>= 100 due to the lack of percision since it surpasses the capability of double and uint64 so you can't test if the number is even.

Solution 2495075

1 Comment

1 Comment

Sivaramarao B on 8 Jun 2020

I think there is a bug in the assertions after 4th one

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

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.

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Problem 44311. Number of Even Elements in Fibonacci Sequence

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Problem 44311. Number of Even Elements in Fibonacci Sequence

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