🌵60. Permutation Sequence
https://leetcode.com/problems/permutation-sequence/
js
/**
* @param {number} n
* @param {number} k
* @return {string}
*/
var getPermutation = function(n, k) {
var fac = [1]
for (let i = 1; i <= n; i++) {
fac[i] = fac[i - 1] * i
}
var str = []
for (let i = 1; i <= n; i++) {
str.push('' + i)
}
var result = []
for (let i = 0; i < n; i++) {
let index = (k - 1) / fac[n - i - 1] >> 0
result.push(str[index])
str.splice(index, 1)
k = (k - 1) % fac[n - i - 1] + 1
}
return result.join('')
}py
class Solution(object):
def getPermutation(self, n, k):
"""
:type n: int
:type k: int
:rtype: str
"""
fac = [1]
for i in range(1, n + 1):
fac.append(fac[-1] * i)
chs = [str(i) for i in range(1, n + 1)]
result = []
for i in range(n):
index = (k - 1) // fac[n - i - 1]
result.append(chs.pop(index))
k = (k - 1) % fac[n - i - 1] + 1
return ''.join(result)