Project Euler 024 #1225

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	/**
	* 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
	}

8 changes: 8 additions & 0 deletions Project-Euler/test/Problem024.test.js

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	import { lexicographicPermutations } from '../Problem024.js'

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

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