freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-10-summation-of-primes.md

id	title	challengeType	forumTopicId	dashedName
5900f3761000cf542c50fe89	Problem 10: Summation of primes	5	301723	problem-10-summation-of-primes

--description--

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below n.

--hints--

primeSummation(17) should return a number.

assert(typeof primeSummation(17) === 'number');

primeSummation(17) should return 41.

assert.strictEqual(primeSummation(17), 41);

primeSummation(2001) should return 277050.

assert.strictEqual(primeSummation(2001), 277050);

primeSummation(140759) should return 873608362.

assert.strictEqual(primeSummation(140759), 873608362);

primeSummation(2000000) should return 142913828922.

assert.strictEqual(primeSummation(2000000), 142913828922);

--seed--

--seed-contents--

function primeSummation(n) {

  return true;
}

primeSummation(2000000);

--solutions--

function primeSummation(n) {
  if (n < 3) { return 0 };
  let nums = [0, 0, 2];
  for (let i = 3; i < n; i += 2){
    nums.push(i);
    nums.push(0);
  }
  let sum = 2;
  for (let i = 3; i < n; i += 2){
    if (nums[i] !== 0){
      sum += nums[i];
      for (let j = i*i; j < n; j += i){
        nums[j] = 0;
      }
    }
  }
  return sum;
}