Problem 69. Find the peak 3n+1 sequence value

Created by Cody Team

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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: 93px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 46.5px; transform-origin: 407px 46.5px; 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: 369px 8px; transform-origin: 369px 8px; unicode-bidi: normal; "><span style="">A Collatz sequence is the sequence where, for a given number n, the next number in the sequence is either n/2 if the number is even or 3n+1 if the number is odd. See</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://in.mathworks.com/matlabcentral/cody/problems/21/"><span style=""><span style="">Problem 21</span></span></a><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: 67.5px 8px; transform-origin: 67.5px 8px; unicode-bidi: normal; "><span style=""> for more information.</span></span></div><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: 384px 8px; transform-origin: 384px 8px; unicode-bidi: normal; "><span style="">Let c(n) be the sequence for n, and p(n) be the peak value of that sequence. For a given threshold nmax, find the highest peak value max(p(n)) for all Collatz sequences starting with integers between 1 and nmax.</span></span></div></div></div>

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Solution Stats

3364 Solutions
1773 Solvers

Last Solution submitted on Jan 19, 2023

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10 Comments

10 Comments

Show 7 older comments

Hariprasad Baburajan on 25 Dec 2018

Nice one

Zoltán Nagy on 26 Apr 2019

Good problem!

Mark McBroom on 10 Jan 2021

good.

Rik on 13 Jan 2021

If you want to add more tests: https://oeis.org/A006884 and https://oeis.org/A006885 contain the relevant sequences.

Tanzil Parvez (Emon) on 3 May 2021

Why the leading solution size is 0 ? Is it for everyone or just me

goc3 on 3 May 2021

@Tanzil Parvez (Emon): the hack solutions (hopefully all) have been deleted from this problem.

Md. Nayem Uddin Biswas on 8 Aug 2022

Wrong test cases! I checked on internet and found all the test cases except case 1 are wrong.

Dyuman Joshi on 8 Aug 2022

The test cases are all correct. You have simply not understood what the question is asking.

Meg Noah on 14 Oct 2022

Broken link in description.

Dyuman Joshi on 14 Oct 2022

Link has been updated.

Solution Comments

1 Comment

1 Comment

A C on 3 Jan 2019

How would I speed this up?
If I input nmax = 2^60, my program cannot finish.

Solution 1088348

1 Comment

1 Comment

yurenchu on 25 Dec 2016

This solution will fail for nmax = 2; so I had to swap the order of two lines. See Solution 1088355.

Solution 329048

1 Comment

1 Comment

Ted on 4 Oct 2013

wrong, corrected in soln 329062

Solution 24293

1 Comment

1 Comment

Peter Wittenberg on 28 Mar 2012

Clever pattern, but still gaming the system. This is not the absolute highest Collatz peak as you go to infinity. Yuval, you should be ashamed of submitting this without apologies.

Solution 13478

4 Comments

4 Comments

Show 1 older comment

Jed F. on 30 Jan 2012

This really doesn't solve the problem it's just gaming the results.

Kevin Holst on 14 Feb 2012

Boo.

Jean-Yves Tinevez on 17 Feb 2012

Ooooooh this is evil.

Peter Wittenberg on 28 Mar 2012

Pathetic

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Problem 69. Find the peak 3n+1 sequence value

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Problem 69. Find the peak 3n+1 sequence value

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