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24.js
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24.js
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JG.solution(24, () => {
/* START
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?
END */
// take all permutations of n-1 and slot the new number in each position, from right to left
let items = []
const max = 9
for (let i = 0; i <= max; i++) {
items = permutations(items, String(i))
}
function permutations (previous, newChar) {
if (!previous.length) return [newChar]
const output = []
for (let i = 0; i <= previous.length - 1; i++) {
for (let j = previous[i].length; j >= 0; j--) {
let item = previous[i].split('')
item.splice(j, 0, newChar)
output.push(item.join(''))
}
}
return output
}
items.sort()
return items[999999]
})