Problem 1509. Fast Fourier transform algorithm

Created by Bob Levy

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<div style = "text-align: start; line-height: 20.4333px; min-height: 0px; white-space: normal; color: rgb(0, 0, 0); font-family: Menlo, Monaco, Consolas, monospace; font-style: normal; font-size: 14px; font-weight: 400; text-decoration: rgb(0, 0, 0); white-space: normal; "><div style="block-size: 144px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 72px; transform-origin: 407px 72px; vertical-align: baseline; "><div style="block-size: 42px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 21px; text-align: left; transform-origin: 384px 21px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 381.5px 8px; transform-origin: 381.5px 8px; unicode-bidi: normal; "><span style="">Your task is to implement the Fast Fourier transform algorithm, without using builtin MATLAB fft commands e.g. fft, fft2, or hardcoded numeric answers in the test case. The test suite employs regular expression matching to reject such solutions.</span></span></div><div style="block-size: 63px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 31.5px; text-align: left; transform-origin: 384px 31.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 373.5px 8px; transform-origin: 373.5px 8px; unicode-bidi: normal; "><span style="">Creative hacking attempts are appreciated. While I will update the test case accordingly, I'll send you some MathWorks swag if you're the first to demonstrate a new way to get the Test Suite to pass (maybe a t-shirt or coffee mug, you'll have to try and see :-) Jose', yours is on the way.</span></span></div><div style="block-size: 21px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 10.5px; text-align: left; transform-origin: 384px 10.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 32.5px 8px; transform-origin: 32.5px 8px; unicode-bidi: normal; "><span style="">reference:</span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 2px 8px; transform-origin: 2px 8px; unicode-bidi: normal; "><span style=""> </span></span><a target='_blank' href = "https://www.mathworks.com/matlabcentral/cody/problems/1509-fast-fourier-transform-algorithm/edit#null"><span style=""><span style="">http://en.wikipedia.org/wiki/Fast_Fourier_transform</span></span></a></div></div></div>

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Solution Stats

458 Solutions
10 Solvers

Last Solution submitted on Jun 24, 2022

Last 200 Solutions

Problem Comments

3 Comments

3 Comments

Selvaraaju Murugesan on 15 May 2013

Some numerical inaccuracies with the test case and the expected output!

G K on 15 May 2013

float tolerance needed ?

Peter Cook on 2 Oct 2014

I'm off by O(10*eps) from the test suite, can you possibly test isequal(single(fft(x)),single(y))

Solution Comments

Solution 280284

2 Comments

2 Comments

Jean-Marie Sainthillier on 14 Jul 2013

I don't know why regexp miss this ...

J.R.! Menzinger on 20 Aug 2013

Very Nice solution!!

hehehe

Solution 244790

3 Comments

3 Comments

J.R.! Menzinger on 15 May 2013

Ok! a little hack on this... ;-)

Bob Levy on 14 Jun 2013

Jose', you've inspired me to make this a bit of a hacking competition. I'll update the test suite to address issues found, but will reward the first to find issues like you have by sending MathWorks swag (maybe a t-shirt or coffee mug, you'll have to try and see :-) Jose', yours is on the way.

J.R.! Menzinger on 9 Jul 2013

I became my t-shirt and my basecap with the post for 3 days... THANK YOU!! ;-)

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