feat: add tech number algorithm

Maths/TechNumber.js

@@ -0,0 +1,26 @@
+/**
+ * @function isTechNumber
+ * @description A tech number is an even digit number where if the number
+ *   is split into two halves, the square of the sum of the two halves
+ *   equals the original number.
+ *   For example, 2025: split into 20 and 25, (20+25)² = 45² = 2025.
+ * @param {number} n - A positive integer with even number of digits
+ * @returns {boolean} - True if n is a tech number, false otherwise
+ * @see https://www.geeksforgeeks.org/tech-number/
+ * @example isTechNumber(2025) => true
+ * @example isTechNumber(3025) => true
+ * @example isTechNumber(1234) => false
+ */
+const isTechNumber = (n) => {
+  if (!Number.isInteger(n) || n < 1) {
+    throw new TypeError('Input must be a positive integer')
+  }
+  const str = String(n)
+  if (str.length % 2 !== 0) return false
+  const half = str.length / 2
+  const left = Number(str.slice(0, half))
+  const right = Number(str.slice(half))
+  return Math.pow(left + right, 2) === n
+}
+
+export { isTechNumber }

Maths/test/TechNumber.test.js

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+import { isTechNumber } from '../TechNumber.js'
+
+describe('isTechNumber', () => {
+  test('2025 is a tech number (20+25=45, 45²=2025)', () => {
+    expect(isTechNumber(2025)).toBe(true)
+  })
+
+  test('3025 is a tech number (30+25=55, 55²=3025)', () => {
+    expect(isTechNumber(3025)).toBe(true)
+  })
+
+  test('9801 is a tech number (98+01=99, 99²=9801)', () => {
+    expect(isTechNumber(9801)).toBe(true)
+  })
+
+  test('1234 is NOT a tech number', () => {
+    expect(isTechNumber(1234)).toBe(false)
+  })
+
+  test('odd digit numbers are NOT tech numbers', () => {
+    expect(isTechNumber(123)).toBe(false)
+  })
+
+  test('100 is NOT a tech number', () => {
+    expect(isTechNumber(100)).toBe(false)
+  })
+
+  test('81 is a tech number (8+1=9, 9²=81)', () => {
+    expect(isTechNumber(81)).toBe(true)
+  })
+
+  test('throws TypeError for zero', () => {
+    expect(() => isTechNumber(0)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for negative input', () => {
+    expect(() => isTechNumber(-2025)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float input', () => {
+    expect(() => isTechNumber(20.25)).toThrow(TypeError)
+  })
+})