Problem 44311. Number of Even Elements in Fibonacci Sequence

Created by Mehmet OZC

Solve Later

{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Find how many even Fibonacci numbers are available in the first d numbers.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Consider the following first 14 numbers</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[1 1 2 3 5 8 13 21 34 55 89 144 233 377 ...]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>4 of them are even.</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

Solve

Solution Stats

2886 Solutions
594 Solvers

Last Solution submitted on Nov 24, 2020

Last 200 Solutions

Problem Comments

4 Comments

4 Comments

Show 1 older comment

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 at 6:56

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 at 22:29

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.

Problem Recent Solvers594

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 44311. Number of Even Elements in Fibonacci Sequence

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers594

Suggested Problems

More from this Author64

Problem Tags

Community Treasure Hunt

Problem 44311. Number of Even Elements in Fibonacci Sequence

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers594

Suggested Problems

More from this Author64

Problem Tags

Community Treasure Hunt

Players