From 35e1fe68d0d6e8be2c2cfdc4dd581faa5128b7e2 Mon Sep 17 00:00:00 2001
From: Alex Popov <aleksborislavskij@gmail.com>
Date: Mon, 31 Oct 2022 19:49:14 +0300
Subject: [PATCH] algorithm: add IntToBase algo and a test for it (#1258)

---
 Maths/IntToBase.js           | 40 ++++++++++++++++++++++++++++++++++++
 Maths/test/IntToBase.test.js | 25 ++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 Maths/IntToBase.js
 create mode 100644 Maths/test/IntToBase.test.js

diff --git a/Maths/IntToBase.js b/Maths/IntToBase.js
new file mode 100644
index 000000000..6ec8a0bab
--- /dev/null
+++ b/Maths/IntToBase.js
@@ -0,0 +1,40 @@
+/**
+ * @function intToBase
+ * @description Convert a number from decimal system to another (till decimal)
+ * @param {Number} number Number to be converted
+ * @param {Number} base Base of new number system
+ * @returns {String} Converted Number
+ * @see [HornerMethod](https://en.wikipedia.org/wiki/Horner%27s_method)
+ * @example
+ * const num1 = 125 // Needs to be converted to the binary number system
+ * gornerScheme(num, 2); // ===> 1111101
+ * @example
+ * const num2 = 125 // Needs to be converted to the octal number system
+ * gornerScheme(num, 8); // ===> 175
+ */
+const intToBase = (number, base) => {
+  if (typeof number !== 'number' || typeof base !== 'number') {
+    throw new Error('Input data must be numbers')
+  }
+  // Zero in any number system is zero
+  if (number === 0) {
+    return '0'
+  }
+  let absoluteValue = Math.abs(number)
+  let convertedNumber = ''
+  while (absoluteValue > 0) {
+    // Every iteration last digit is taken away
+    // and added to the previous one
+    const lastDigit = absoluteValue % base
+    convertedNumber = lastDigit + convertedNumber
+    absoluteValue = Math.trunc(absoluteValue / base)
+  }
+  // Result is whether negative or positive,
+  // depending on the original value
+  if (number < 0) {
+    convertedNumber = '-' + convertedNumber
+  }
+  return convertedNumber
+}
+
+export { intToBase }
diff --git a/Maths/test/IntToBase.test.js b/Maths/test/IntToBase.test.js
new file mode 100644
index 000000000..002dde6af
--- /dev/null
+++ b/Maths/test/IntToBase.test.js
@@ -0,0 +1,25 @@
+import { intToBase } from '../intToBase'
+
+describe('Int to Base', () => {
+  test('Conversion to the binary system', () => {
+    expect(intToBase(210, 2)).toEqual('11010010')
+    expect(intToBase(-210, 2)).toEqual('-11010010')
+  })
+  test('Conversion to the system with base 5', () => {
+    expect(intToBase(210, 5)).toEqual('1320')
+    expect(intToBase(-210, 5)).toEqual('-1320')
+  })
+  test('Conversion to the octal system', () => {
+    expect(intToBase(210, 8)).toEqual('322')
+    expect(intToBase(-210, 8)).toEqual('-322')
+  })
+  test('Output is 0', () => {
+    expect(intToBase(0, 8)).toEqual('0')
+    expect(intToBase(0, 8)).toEqual('0')
+  })
+  test('Throwing an exception', () => {
+    expect(() => intToBase('string', 2)).toThrow()
+    expect(() => intToBase(10, 'base')).toThrow()
+    expect(() => intToBase(true, false)).toThrow()
+  })
+})