Python 刷Leetcode题库，顺带学英语单词（18）

Permutation Sequence

The set [1,2,3,...,*n*] contains a total of n! unique permutations.   [#60]

By listing and labeling all of the permutations in order, we get the following sequence for n = 3:

1. "123"

2. "132"

3. "213"

4. "231"

5. "312"

6. "321"

Given n and k, return the kth permutation sequence.

Note:

Given n will be between 1 and 9 inclusive.

Given k will be between 1 and n! inclusive.

Examples:
Input: n = 3, k = 3
Output: "213"
Input: n = 4, k = 9
Output: "2314"