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60. Permutation Sequence.go
60. Permutation Sequence_test.go
README.md

README.md

60. Permutation Sequence

题目

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"

题目大意

给出集合 [1,2,3,…,n],其所有元素共有 n! 种排列。

按大小顺序列出所有排列情况,并一一标记,当 n = 3 时, 所有排列如下:"123","132","213","231","312","321",给定 n 和 k,返回第 k 个排列。

解题思路

  • 用 DFS 暴力枚举,这种做法时间复杂度特别高,想想更优的解法。
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