0060-permutation-sequence.adoc

60. Permutation Sequence

{leetcode}/problems/permutation-sequence/[LeetCode - Permutation Sequence^]

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 k^th 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"

解题分析

不需要生成所有的全排列。如图，通过剪枝，只需要生成需要的排列的路径即可。

这里的重点是如何剪枝！

思考题

对回溯再推敲推敲！

参考资料

1. 深度优先遍历 + 剪枝、双链表模拟 - 第k个排列 - 力扣（LeetCode）

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:

• "123"

• "132"

• "213"

• "231"

• "312"

• "321"

Given n and k, return the k^th 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"

link:{sourcedir}/_0060_PermutationSequence.java[role=include]