freeCodeCamp

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id	challengeType	title
5900f5151000cf542c510028	5	Problem 425: Prime connection

Description

Two positive numbers A and B are said to be connected (denoted by "A ↔ B") if one of these conditions holds: (1) A and B have the same length and differ in exactly one digit; for example, 123 ↔ 173. (2) Adding one digit to the left of A (or B) makes B (or A); for example, 23 ↔ 223 and 123 ↔ 23.

We call a prime P a 2's relative if there exists a chain of connected primes between 2 and P and no prime in the chain exceeds P.

For example, 127 is a 2's relative. One of the possible chains is shown below: 2 ↔ 3 ↔ 13 ↔ 113 ↔ 103 ↔ 107 ↔ 127 However, 11 and 103 are not 2's relatives.

Let F(N) be the sum of the primes ≤ N which are not 2's relatives. We can verify that F(103) = 431 and F(104) = 78728.

Find F(107).

Instructions

Tests

tests:
  - text: <code>euler425()</code> should return 46479497324.
    testString: assert.strictEqual(euler425(), 46479497324);

Challenge Seed

function euler425() {
  // Good luck!
  return true;
}

euler425();

Solution

// solution required

1.4 KiB Raw Blame History