merge: Decimal Expansion (#787)

* Add Math function for representing the decimal expansion of a given fraction (decimal or any base from 2 to 10). * Auto-update DIRECTORY.md * DecimalExpansion Jest tests. * chore: trigger update * Auto-update DIRECTORY.md * Auto-update DIRECTORY.md * chore: trigger checks Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Rak Laptudirm <rak@laptudirm.com> Co-authored-by: Rak Laptudirm <raklaptudirm@gmail.com>
2025-07-05 00:01:37 +08:00 · 2022-04-02 17:10:57 +02:00
parent 6f33f990f2
commit 2be0fdcb49
3 changed files with 267 additions and 0 deletions
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@ -18,6 +18,8 @@
  * [LFUCache](https://github.com/TheAlgorithms/Javascript/blob/master/Cache/LFUCache.js)
  * [LRUCache](https://github.com/TheAlgorithms/Javascript/blob/master/Cache/LRUCache.js)
  * [Memoize](https://github.com/TheAlgorithms/Javascript/blob/master/Cache/Memoize.js)
+  * test
+    * [cacheTest](https://github.com/TheAlgorithms/Javascript/blob/master/Cache/test/cacheTest.js)

 ## Cellular-Automata
  * [ConwaysGameOfLife](https://github.com/TheAlgorithms/Javascript/blob/master/Cellular-Automata/ConwaysGameOfLife.js)
@ -65,11 +67,13 @@
  * Graph
    * [Graph](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Graph/Graph.js)
    * [Graph2](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Graph/Graph2.js)
+    * [Graph3](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Graph/Graph3.js)
  * Heap
    * [MaxHeap](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Heap/MaxHeap.js)
    * [MinHeap](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Heap/MinHeap.js)
    * [MinPriorityQueue](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Heap/MinPriorityQueue.js)
  * Linked-List
+    * [AddTwoNumbers](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Linked-List/AddTwoNumbers.js)
    * [CycleDetection](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Linked-List/CycleDetection.js)
    * [DoublyLinkedList](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Linked-List/DoublyLinkedList.js)
    * [RotateListRight](https://github.com/TheAlgorithms/Javascript/blob/master/Data-Structures/Linked-List/RotateListRight.js)
@ -143,6 +147,7 @@
  * [Abs](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/Abs.js)
  * [AliquotSum](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/AliquotSum.js)
  * [Area](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/Area.js)
+  * [ArithmeticGeometricMean](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/ArithmeticGeometricMean.js)
  * [ArmstrongNumber](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/ArmstrongNumber.js)
  * [AverageMean](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/AverageMean.js)
  * [AverageMedian](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/AverageMedian.js)
@ -153,6 +158,7 @@
  * [CheckKishnamurthyNumber](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/CheckKishnamurthyNumber.js)
  * [Coordinate](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/Coordinate.js)
  * [CoPrimeCheck](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/CoPrimeCheck.js)
+  * [DecimalExpansion](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/DecimalExpansion.js)
  * [DecimalIsolate](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/DecimalIsolate.js)
  * [DegreeToRadian](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/DegreeToRadian.js)
  * [EulerMethod](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/EulerMethod.js)
@ -168,6 +174,7 @@
  * [FindHcf](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/FindHcf.js)
  * [FindLcm](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/FindLcm.js)
  * [FindMin](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/FindMin.js)
+  * [FindMinIterator](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/FindMinIterator.js)
  * [GetEuclidGCD](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/GetEuclidGCD.js)
  * [GridGet](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/GridGet.js)
  * [IsDivisible](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/IsDivisible.js)
@ -290,6 +297,7 @@
  * [AlternativeStringArrange](https://github.com/TheAlgorithms/Javascript/blob/master/String/AlternativeStringArrange.js)
  * [CheckAnagram](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckAnagram.js)
  * [CheckCamelCase](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckCamelCase.js)
+  * [CheckExceeding](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckExceeding.js)
  * [CheckFlatCase](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckFlatCase.js)
  * [CheckKebabCase](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckKebabCase.js)
  * [CheckPalindrome](https://github.com/TheAlgorithms/Javascript/blob/master/String/CheckPalindrome.js)
--- a/Maths/DecimalExpansion.js
+++ b/Maths/DecimalExpansion.js
@ -0,0 +1,67 @@
+/**
+ * @author Eric Lavault <https://github.com/lvlte>
+ *
+ * Represents the decimal (or binary, octal, any base from 2 to 10) expansion
+ * of a/b using euclidean division.
+ *
+ * Because this function is recursive, it may throw an error when reaching the
+ * maximum call stack size.
+ *
+ * Returns an array containing : [
+ *  0: integer part of the division
+ *  1: array of decimals (if any, or an empty array)
+ *  2: indexOf 1st cycle digit in decimals array if a/b is periodic, or undef.
+ * ]
+ *
+ * @see https://mathworld.wolfram.com/DecimalExpansion.html
+ *
+ * @param {number} a
+ * @param {number} b
+ * @param {number} [base=10]
+ * @returns {array}
+ */
+export function decExp (a, b, base = 10, exp = [], d = {}, dlen = 0) {
+  if (base < 2 || base > 10) {
+    throw new RangeError('Unsupported base. Must be in range [2, 10]')
+  }
+
+  if (a === 0) {
+    return [0, [], undefined]
+  }
+
+  if (a === b && dlen === 0) {
+    return [1, [], undefined]
+  }
+
+  // d contains the dividends used so far and the corresponding index of its
+  // euclidean division by b in the expansion array.
+  d[a] = dlen++
+
+  if (a < b) {
+    exp.push(0)
+    return decExp(a * base, b, base, exp, d, dlen)
+  }
+
+  // Euclid's division lemma : a = bq + r
+  const r = a % b
+  const q = (a - r) / b
+
+  // Decimal expansion (1st element is the integer part)
+  exp.push(+q.toString(base))
+
+  if (r === 0) {
+    // got a regular number (division terminates)
+    return [exp[0], exp.slice(1), undefined]
+  }
+
+  // For the next iteration
+  a = r * base
+
+  // Check if `a` has already been used as a dividend, in which case it means
+  // the expansion is periodic.
+  if (a in d) {
+    return [exp[0], exp.slice(1), d[a] - 1]
+  }
+
+  return decExp(a, b, base, exp, d, dlen)
+}
--- a/Maths/test/DecimalExpansion.test.js
+++ b/Maths/test/DecimalExpansion.test.js
@ -0,0 +1,192 @@
+import { decExp } from '../DecimalExpansion'
+
+/**
+ * Decimal
+ */
+
+describe('Finite Decimal Expansion', () => {
+  it('1/2 = 0.5', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 2)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([5])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('1/5 = 0.2', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 5)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([2])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('1/8 = 0.125', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 8)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([1, 2, 5])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('255/40 = 6.375', () => {
+    const [integer, decimals, cycleIndex] = decExp(255, 40)
+    expect(integer).toBe(6)
+    expect(decimals).toEqual([3, 7, 5])
+    expect(cycleIndex).toBeUndefined()
+  })
+})
+
+describe('Repeating Decimal Expansion', () => {
+  it('1/3 = 0.(3)', () => {
+    expect(decExp(1, 3)).toStrictEqual([0, [3], 0])
+  })
+
+  it('1/6 = 0.1(6)', () => {
+    expect(decExp(1, 6)).toStrictEqual([0, [1, 6], 1])
+  })
+
+  it('1/7 = 0.(142857)', () => {
+    expect(decExp(1, 7)).toStrictEqual([0, [1, 4, 2, 8, 5, 7], 0])
+  })
+})
+
+/**
+ * Binary
+ */
+
+describe('Finite Binary Expansion', () => {
+  it('1/2 = 0.1₂', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 2, 2)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([1])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('1/8 = 0.001₂', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 8, 2)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([0, 0, 1])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('255/40 = 110.011₂', () => {
+    const [integer, decimals, cycleIndex] = decExp(255, 40, 2)
+    expect(integer).toBe(110)
+    expect(decimals).toEqual([0, 1, 1])
+    expect(cycleIndex).toBeUndefined()
+  })
+})
+
+describe('Repeating Binary Expansion', () => {
+  it('1/3 = 0.(01)₂', () => {
+    expect(decExp(1, 3, 2)).toStrictEqual([0, [0, 1], 0])
+  })
+
+  it('1/5 = 0.(0011)₂', () => {
+    expect(decExp(1, 5, 2)).toStrictEqual([0, [0, 0, 1, 1], 0])
+  })
+
+  it('1/6 = 0.0(01)₂', () => {
+    expect(decExp(1, 6, 2)).toStrictEqual([0, [0, 0, 1], 1])
+  })
+
+  it('1/7 = 0.(001)₂', () => {
+    expect(decExp(1, 7, 2)).toStrictEqual([0, [0, 0, 1], 0])
+  })
+})
+
+/**
+ * Octal
+ */
+
+describe('Finite Octal Expansion', () => {
+  it('1/2 = 0.4₈', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 2, 8)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([4])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('1/8 = 0.1₈', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 8, 8)
+    expect(integer).toBe(0)
+    expect(decimals).toEqual([1])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('255/40 = 6.3₈', () => {
+    const [integer, decimals, cycleIndex] = decExp(255, 40, 8)
+    expect(integer).toBe(6)
+    expect(decimals).toEqual([3])
+    expect(cycleIndex).toBeUndefined()
+  })
+})
+
+describe('Repeating Octal Expansion', () => {
+  it('1/3 = 0.(25)₈', () => {
+    expect(decExp(1, 3, 8)).toStrictEqual([0, [2, 5], 0])
+  })
+
+  it('1/5 = 0.(1463)₈', () => {
+    expect(decExp(1, 5, 8)).toStrictEqual([0, [1, 4, 6, 3], 0])
+  })
+
+  it('1/6 = 0.1(25)₈', () => {
+    expect(decExp(1, 6, 8)).toStrictEqual([0, [1, 2, 5], 1])
+  })
+
+  it('1/7 = 0.(1)₈', () => {
+    expect(decExp(1, 7, 8)).toStrictEqual([0, [1], 0])
+  })
+})
+
+/**
+ * Integers
+ */
+
+describe('Integers', () => {
+  it('1/1 = 1', () => {
+    const [integer, decimals, cycleIndex] = decExp(1, 1)
+    expect(integer).toBe(1)
+    expect(decimals).toStrictEqual([])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('5/5 = 1', () => {
+    const [integer, decimals, cycleIndex] = decExp(5, 5)
+    expect(integer).toBe(1)
+    expect(decimals).toStrictEqual([])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('2/1 = 2', () => {
+    const [integer, decimals, cycleIndex] = decExp(2, 1)
+    expect(integer).toBe(2)
+    expect(decimals).toStrictEqual([])
+    expect(cycleIndex).toBeUndefined()
+  })
+
+  it('9/3 = 3', () => {
+    const [integer, decimals, cycleIndex] = decExp(9, 3)
+    expect(integer).toBe(3)
+    expect(decimals).toStrictEqual([])
+    expect(cycleIndex).toBeUndefined()
+  })
+})
+
+/**
+ * Unsupported base
+ */
+
+describe('Throws on unsupported base', () => {
+  it('negative base', () => {
+    expect(() => decExp(1, 1, -2)).toThrow(RangeError)
+  })
+  it('base 0', () => {
+    expect(() => decExp(1, 1, 0)).toThrow(RangeError)
+  })
+  it('base 1', () => {
+    expect(() => decExp(1, 1, 1)).toThrow(RangeError)
+  })
+  it('base 11', () => {
+    expect(() => decExp(1, 1, 11)).toThrow(RangeError)
+  })
+})