FilesExpand file tree

 master

/

Problem035.js

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

39 lines (35 loc) · 1.28 KB

 master

/

Problem035.js

Top

File metadata and controls

• Code
• Blame

39 lines (35 loc) · 1.28 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

/**

* Problem 35 - Circular primes

*

* @see {@link https://projecteuler.net/problem=35}

*

* The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.

* There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.

* How many circular primes are there below one million?

*

* @author ddaniel27

*/

import { sieveOfEratosthenes } from '../Maths/SieveOfEratosthenesIntArray'

function problem35(n) {

if (n < 2) {

throw new Error('Invalid input')

}

// Get a list of primes without 0, 2, 4, 5, 6, 8; this discards the circular primes 2 & 5

const list = sieveOfEratosthenes(n).filter(

(prime) => !prime.toString().match(/[024568]/)

)

const result = list.filter((number, _idx, arr) => {

const str = String(number)

for (let i = 0; i < str.length; i++) {

// Get all rotations of the number

const rotation = str.slice(i) + str.slice(0, i)

if (!arr.includes(Number(rotation))) {

// Check if the rotation is prime

return false

}

}

return true // If all rotations are prime, then the number is circular prime

})

return result.length + 2 // Add 2 to the result because the circular primes 2 & 5 were discarded

}

export { problem35 }