Problem 241. Project Euler: Problem 7, Nth prime

Created by Doug Hull

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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: 81px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 40.5px; transform-origin: 407px 40.5px; vertical-align: baseline; "><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: 298px 8px; transform-origin: 298px 8px; unicode-bidi: normal; "><span style="">By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.</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: 97.5px 8px; transform-origin: 97.5px 8px; unicode-bidi: normal; "><span style="">What is the Nth prime number?</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: 41.5px 8px; transform-origin: 41.5px 8px; unicode-bidi: normal; "><span style="">Thank you to</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 = "/#null"><span style=""><span style="">Project Euler Problem 7</span></span></a></div></div></div>

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Solution Stats

2897 Solutions
1114 Solvers

Last Solution submitted on Jan 29, 2023

Last 200 Solutions

Problem Comments

5 Comments

5 Comments

Show 2 older comments

John D'Errico on 22 Feb 2018

Aw drat. I was going to submit the n'th prime problem until I saw this.

John D'Errico on 22 Feb 2018

Sadly, I see there are too few test cases, and the problem is too easy to cook.

Jiawei Gong on 7 Apr 2020

why 'nthprime' not allowed?

Sachin Mysore on 15 Mar 2022

There's a really easy way to cheese this problem if you find it. It happens to lie in the comment John D'Errico made about there being too few test cases. I'd encourage you to do the problem properly without such a cheese

Aadhithya T V on 14 Jan 2023 at 3:40

A good problem!

Solution Comments

Solution 10329575

1 Comment

1 Comment

Chris Joyce on 29 Jan 2023 at 7:43

The constraints put on the solution such as not using if statements and not using nthprime should be stated in the problem. I had to look at the tests to work out the rules that the author wanted us to play to.

Solution 1688905

1 Comment

1 Comment

Roche de Guzman on 8 Dec 2018

Another great problem!

Solution 1178077

1 Comment

1 Comment

yurenchu on 2 May 2017

This solution doesn't use any of the built-in MATLAB functions primes() or isprime(). It works for all integers N > 0, and requires only (N^0.75) iterations.

Solution 292972

2 Comments

2 Comments

Ramy Mohamed on 31 Jul 2013

I do not know how the size are computed. Would someone please tell me?. Thanks in advance.

David Verrelli on 12 Mar 2018

See https://au.mathworks.com/matlabcentral/about/cody/#solve_problems for basic concept. The best way to figure out the details is from experience — just try different alternatives.

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Problem 241. Project Euler: Problem 7, Nth prime

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Problem 241. Project Euler: Problem 7, Nth prime

Solution Stats

Last 200 Solutions

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Problem Recent Solvers1114

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