feat(maths): finishes calculate median (#114)

* feat: add calculate median

* Resolving comments

* feat: improvements & resolves requested changes

---------

Co-authored-by: syedjafer <[email protected]>

Author: zFl4wless

Maths/CalculateMedian.ts

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+/**
+ * @function calculateMedian
+ * @description This function will find the median value of an array of numbers.
+ * @param {number[]} numbers Sorted array of numeric values.
+ * @return {number} The median of input numbers.
+ * @see https://en.wikipedia.org/wiki/Median
+ * @example calculateMedian([1, 2, 4, 5, 8]) = 4
+ * @example calculateMedian([1, 2, 4, 5]) = 3
+ */
+
+export const calculateMedian = (numbers: number[]): number => {
+    if (numbers.length < 1) {
+        throw new TypeError("Input array must contain at least one number.");
+    }
+
+    const totalNumbers = numbers.length;
+
+    if (totalNumbers % 2 === 0) {
+        let index = totalNumbers / 2;
+        return (numbers[index - 1] + numbers[index]) / 2;
+    } else {
+        let index = (totalNumbers + 1) / 2;
+        return numbers[index - 1];
+    }
+};

Maths/test/CalculateMedian.test.ts

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+import { calculateMedian } from "../CalculateMedian";
+
+describe("Tests for CalculateMedian", () => {
+    it("should be a function", () => {
+        expect(typeof calculateMedian).toEqual("function");
+    });
+
+    it("should throw error for invalid input", () => {
+        expect(() => calculateMedian([])).toThrowError(
+            "Input array must contain at least one number."
+        );
+    });
+
+    it("should return the median of an array of numbers - even length", () => {
+        const medianFunction = calculateMedian([1, 2, 3, 4]);
+        expect(medianFunction).toBe(2.5);
+    });
+
+    it("should return the median of an array of numbers - odd length", () => {
+        const medianFunction = calculateMedian([1, 2, 3, 4, 6, 8, 9]);
+        expect(medianFunction).toBe(4);
+    });
+});