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Problem024.js
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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
}