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Problem 47: Distinct primes factors

curriculum/challenges/english/blocks/project-euler-problems-1-to-100/5900f39c1000cf542c50feae.md

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--description--

The first two consecutive numbers to have two distinct prime factors are:

<div style='padding-left: 4em;'> 14 = 2 × 7

15 = 3 × 5

</div>

The first three consecutive numbers to have three distinct prime factors are:

<div style='padding-left: 4em;'> 644 = 2<sup>2</sup> × 7 × 23

645 = 3 × 5 × 43

646 = 2 × 17 × 19

</div>

Find the first four consecutive integers to have four distinct prime factors each. What is the first of these numbers?

--hints--

distinctPrimeFactors(2, 2) should return a number.

js
assert(typeof distinctPrimeFactors(2, 2) === 'number');

distinctPrimeFactors(2, 2) should return 14.

js
assert.strictEqual(distinctPrimeFactors(2, 2), 14);

distinctPrimeFactors(3, 3) should return 644.

js
assert.strictEqual(distinctPrimeFactors(3, 3), 644);

distinctPrimeFactors(4, 4) should return 134043.

js
assert.strictEqual(distinctPrimeFactors(4, 4), 134043);

--seed--

--seed-contents--

js
function distinctPrimeFactors(targetNumPrimes, targetConsecutive) {

  return true;
}

distinctPrimeFactors(4, 4);

--solutions--

js
function distinctPrimeFactors(targetNumPrimes, targetConsecutive) {
  const primeLimit = targetNumPrimes * targetConsecutive * 10000;
  const numFactors = Array(primeLimit).fill(0);

  let numConsecutive = 0;
  for (let i = 2; i < primeLimit; i++) {
    if (numFactors[i] === targetNumPrimes) {
      // Current number is composite with target num factors
      numConsecutive++;
      if (numConsecutive === targetConsecutive) {
        return i - numConsecutive + 1;
      }
    } else {
      // Current number is not matching composite
      numConsecutive = 0;
      if (numFactors[i] === 0) {
        // Current number is prime
        for (let j = i; j < primeLimit; j += i) {
          numFactors[j]++;
        }
      }
    }
  }
}