Oct 23, 2022
diff --git a/Project-Euler/Problem024.js b/Project-Euler/Problem024.js
 /**
 * Problem 24 - Lexicographic Permutations
 *
 * @see {@link https://projecteuler.net/problem=24}
 *
 * A permutation is an ordered arrangement of objects. For example, 3124 is one
 * possible permutation of the digits 1, 2, 3 and 4. If all of the permutations
 * are listed numerically or alphabetically, we call it lexicographic order.
 * The lexicographic permutations of 0, 1 and 2 are:
 *
 * 012   021   102   120   201   210
 *
 * What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?
 */

 export function lexicographicPermutations () {
  const factorial = [1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
  const digits = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  let millionthCounter = 999999
  let result = ''

  for (let i = digits.length - 1; i >= 0; i--) {
    const permutation = (millionthCounter / factorial[i]) | 0

    millionthCounter %= factorial[i]
    result += digits[permutation]

    digits.splice(permutation, 1)
  }

  return result
 }
diff --git a/Project-Euler/test/Problem024.test.js b/Project-Euler/test/Problem024.test.js
 import { lexicographicPermutations } from '../Problem024.js'

 describe('checking Lexicographic Permutations', () => {
  // Project Euler Lexicographic Permutations
  test('Test Lexicographic Permutations', () => {
    expect(lexicographicPermutations()).toBe('2783915460')
  })
 })
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,32 @@
		/**
		* Problem 24 - Lexicographic Permutations
		*
		* @see {@link https://projecteuler.net/problem=24}
		*
		* A permutation is an ordered arrangement of objects. For example, 3124 is one
		* possible permutation of the digits 1, 2, 3 and 4. If all of the permutations
		* are listed numerically or alphabetically, we call it lexicographic order.
		* The lexicographic permutations of 0, 1 and 2 are:
		*
		* 012 021 102 120 201 210
		*
		* What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?
		*/

		export function lexicographicPermutations () {
		const factorial = [1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
		const digits = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
		let millionthCounter = 999999
		let result = ''

		for (let i = digits.length - 1; i >= 0; i--) {
		const permutation = (millionthCounter / factorial[i]) \| 0

		millionthCounter %= factorial[i]
		result += digits[permutation]

		digits.splice(permutation, 1)
		}

		return result
		}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,8 @@
		import { lexicographicPermutations } from '../Problem024.js'

		describe('checking Lexicographic Permutations', () => {
		// Project Euler Lexicographic Permutations
		test('Test Lexicographic Permutations', () => {
		expect(lexicographicPermutations()).toBe('2783915460')
		})
		})