algorithm: sieve (TheAlgorithms#1205)

ddaniel27 · web-flow · commit 0084acf2d4dc · 2022-10-20T16:50:37.000+05:30
diff --git a/Maths/SieveOfEratosthenesIntArray.js b/Maths/SieveOfEratosthenesIntArray.js
@@ -0,0 +1,22 @@
+/**
+ * Function to get all prime numbers below a given number
+ * This function returns an array of prime numbers
+ * @see {@link https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes}
+ */
+
+function sieveOfEratosthenes (max) {
+  const sieve = []
+  const primes = []
+
+  for (let i = 2; i <= max; ++i) {
+    if (!sieve[i]) { // If i has not been marked then it is prime
+      primes.push(i)
+      for (let j = i << 1; j <= max; j += i) { // Mark all multiples of i as non-prime
+        sieve[j] = true
+      }
+    }
+  }
+  return primes
+}
+
+export { sieveOfEratosthenes }
diff --git a/Maths/test/SieveOfEratosthenesIntArray.test.js b/Maths/test/SieveOfEratosthenesIntArray.test.js
@@ -0,0 +1,12 @@
+import { sieveOfEratosthenes } from '../SieveOfEratosthenesIntArray'
+import { PrimeCheck } from '../PrimeCheck'
+
+describe('should return an array of prime numbers', () => {
+  it('should have each element in the array as a prime numbers', () => {
+    const n = 100
+    const primes = sieveOfEratosthenes(n)
+    primes.forEach(prime => {
+      expect(PrimeCheck(prime)).toBeTruthy()
+    })
+  })
+})
