freeCodeCamp

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Raw Blame History

id	challengeType	title	forumTopicId
5900f3a61000cf542c50feb9	5	Problem 58: Spiral primes	302169

Description

Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed. 37 36 35 34 33 32 31 38 17 16 15 14 13 30 39 18 5 4 3 12 29 40 19 6 1 2 11 28 41 20 7 8 9 10 27 42 21 22 23 24 25 2643 44 45 46 47 48 49 It is interesting to note that the odd squares lie along the bottom right diagonal, but what is more interesting is that 8 out of the 13 numbers lying along both diagonals are prime; that is, a ratio of 8/13 ≈ 62%. If one complete new layer is wrapped around the spiral above, a square spiral with side length 9 will be formed. If this process is continued, what is the side length of the square spiral for which the ratio of primes along both diagonals first falls below 10%?

Instructions

Tests

tests:
  - text: <code>euler58()</code> should return 26241.
    testString: assert.strictEqual(euler58(), 26241);

Challenge Seed

function euler58() {
  // Good luck!
  return true;
}

euler58();

Solution

// solution required

1.4 KiB Raw Blame History