merge: Add LinearSieve.js (TheAlgorithms#828)

Author: nella17

Maths/LinearSieve.js

@@ -0,0 +1,24 @@
+const LinearSieve = (n) => {
+  /*
+   * Calculates prime numbers till a number n
+   * Time Complexity: O(n)
+   * Explanation: https://cp-algorithms.com/algebra/prime-sieve-linear.html
+   * :param n: Number up to which to calculate primes
+   * :return: A list containing only primes
+   */
+  const isnPrime = new Array(n + 1)
+  isnPrime[0] = isnPrime[1] = true
+  const primes = []
+  for (let i = 2; i <= n; i++) {
+    if (!isnPrime[i]) primes.push(i)
+    for (const p of primes) {
+      const k = i * p
+      if (k > n) break
+      isnPrime[k] = true
+      if (i % p === 0) break
+    }
+  }
+  return primes
+}
+
+export { LinearSieve }

Maths/test/LinearSieve.test.js

@@ -0,0 +1,16 @@
+import { LinearSieve } from '../LinearSieve'
+import { PrimeCheck } from '../PrimeCheck'
+
+describe('LinearSieve', () => {
+  it('should return primes below 100', () => {
+    expect(LinearSieve(100)).toEqual([2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97])
+  })
+
+  it('should return primes only', () => {
+    const n = 100000
+    const primes = LinearSieve(n)
+    for (const p of primes) {
+      expect(PrimeCheck(p)).toBeTruthy()
+    }
+  })
+})