feat: add prime factorization algorithm (#214)

Author: ayoubc

maths/prime_factorization.ts

@@ -0,0 +1,27 @@
+/**
+ * @description Get exponenets of each prime number in factorization of a number n
+ * @param {number} n - A natural number.
+ * @return {Map<number, number>} - factorization of number n.
+ * @see https://en.wikipedia.org/wiki/Integer_factorization
+ * @example factorize(4) = Map {2 => 2}
+ * @example factorize(5) = Map {5 => 1}
+ */
+export const factorize = (n: number): Map<number, number> => {
+    let result: Map<number, number> = new Map();
+
+    for (let i = 2; i * i <= n; i++) {
+        while (n % i == 0) {
+            let occurence = result.get(i);
+            if (!occurence) occurence = 0;
+            result.set(i, occurence + 1);
+            n = n / i;
+        }
+    }
+    if (n > 1) {
+        let occurence = result.get(n);
+        if (!occurence) occurence = 0;
+        result.set(n, occurence + 1);
+    }
+
+    return result;
+};

maths/test/prime_factorization.test.ts

@@ -0,0 +1,26 @@
+import { factorize } from "../prime_factorization";
+
+
+interface TestCase {
+    n: number;
+    expected: Map<number, number>
+}
+
+const cases: TestCase[] = [
+    {n: 4, expected: new Map([[2, 2]])},
+    {n: 5, expected: new Map([[5, 1]])},
+    {n: 7, expected: new Map([[7, 1]])},
+    {n: 10, expected: new Map([[2, 1], [5, 1]])},
+    {n: 999, expected: new Map([[3, 3], [37, 1]])},
+    {n: 999999999999878, expected: new Map([[2, 1], [19, 1], [26315789473681, 1]])},
+];
+
+describe("factorize", () => {
+
+    test.each(cases)(
+        "prime factorization of $n should be $expected",
+        ({n, expected}) => {
+            expect(factorize(n)).toEqual(expected);
+        },
+    );
+});