freeCodeCamp/problem-7-10001st-prime.english.md at 0498e27902bb8d355d3bb381bc1ba9a445d81fc5

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Oliver Eyton-Williams e4a229187e fix: speed up tests

Either improved the algorithm or reduced the difficulty for the slowest
tests. All these pass with testProtectTimeout = 500, so should be safe
on most machines with the current timeout of 2500.

2020-01-03 11:41:52 +05:30

1.5 KiB

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id, challengeType, title, forumTopicId

id	challengeType	title	forumTopicId
5900f3731000cf542c50fe86	5	Problem 7: 10001st prime	302182

Description

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the nth prime number?

Instructions

Tests

tests:
  - text: <code>nthPrime(6)</code> should return 13.
    testString: assert.strictEqual(nthPrime(6), 13);
  - text: <code>nthPrime(10)</code> should return 29.
    testString: assert.strictEqual(nthPrime(10), 29);
  - text: <code>nthPrime(100)</code> should return 541.
    testString: assert.strictEqual(nthPrime(100), 541);
  - text: <code>nthPrime(1000)</code> should return 7919.
    testString: assert.strictEqual(nthPrime(1000), 7919);
  - text: <code>nthPrime(10001)</code> should return 104743.
    testString: assert.strictEqual(nthPrime(10001), 104743);

Challenge Seed

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

nthPrime(10001);

Solution

const nthPrime = n => {
  let pN = 2;
  let step = 0;
  while (step < n) {
    let isPrime = true;
    let rootN = Math.sqrt(pN);
    for (let i = 2; i <= rootN; i++) {
      if (!(pN % i)) {
        isPrime = false;
        break;
      }
    }
    isPrime ? step++ : '';
    pN++;
  }
  return pN - 1;
}

1.5 KiB Raw Blame History