leetcode0060

60. Permutation Sequence

Description

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

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.

Example 1:

Input: n = 3, k = 3
Output: "213"

Example 2:

Input: n = 4, k = 9
Output: "2314"

思路

每一次循环都是 (n-1)! 个数，当前第一个数即 k 包含多少的完整循环，然后从切片索引中取出，下一个 k 是完整循环之后的余数，然后递归查找下一个数。

康托展开