Primal number square root

Author: edignot

src/pirmal-numbers/primal-number.test.js

@@ -1,13 +1,25 @@
-import isNumberPrime from "./primal-numbers";
+import { isNumberPrime, isNUmberPrimeMath } from "./primal-numbers";
 
-describe("Is 4 prime", () => {
-    test("2nd element of fibonacci sequence", () => {
+describe("Is number prime", () => {
+    test("Is 4 prime number", () => {
         expect(isNumberPrime(4)).toBe(false);
     });
-    test("2nd element of fibonacci sequence", () => {
+    test("Is 17 prime number", () => {
         expect(isNumberPrime(17)).toBe(true);
     });
-    test("2nd element of fibonacci sequence", () => {
+    test("Is 97 prime number", () => {
         expect(isNumberPrime(97)).toBe(true);
     });
 });
+
+describe("Is number prime Math", () => {
+    test("Is 4 prime number", () => {
+        expect(isNumberPrimeMath(4)).toBe(false);
+    });
+    test("Is 17 prime number", () => {
+        expect(isNumberPrimeMath(17)).toBe(true);
+    });
+    test("Is 97 prime number", () => {
+        expect(isNumberPrimeMath(97)).toBe(true);
+    });
+});

src/pirmal-numbers/primal-numbers.js

@@ -1,14 +1,19 @@
 // Problem: Find if given number is a prime number or not. Return true or false
 // Details: Prime number can be divided by 1 or itself
 
-// Time complexity:
-
-const isNumberPrime = (num) => {
+// Time complexity: if input number is 1 or 2 -> O(1), if input number > 2 -> O(n), but if number is divided by 2 even though it's big e.g. 1000000000... , it's O(1) too, because it stops running immediately
+export const isNumberPrime = (num) => {
     let isPrime = true;
     for (let i = 2; i < num; i++) {
         if (num % i === 0) isPrime = false;
     }
     return isPrime;
 };
 
-export default isNumberPrime;
+// Algorithm optimization with Math.sqrt()
+export const isNumberPrimeMath = (num) => {
+    for (let i = 0; i < Math.sqrt(num); i++) {
+        if (num % i === 0) return false;
+    }
+    return true;
+};