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48 lines
1.0 KiB
Markdown
Executable File
48 lines
1.0 KiB
Markdown
Executable File
# [60. Permutation Sequence](https://leetcode.com/problems/permutation-sequence/)
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## 题目
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The set `[1,2,3,...,*n*]` contains a total of *n*! unique permutations.
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By listing and labeling all of the permutations in order, we get the following sequence for *n* = 3:
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1. `"123"`
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2. `"132"`
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3. `"213"`
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4. `"231"`
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5. `"312"`
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6. `"321"`
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Given *n* and *k*, return the *k*th permutation sequence.
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**Note:**
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- Given *n* will be between 1 and 9 inclusive.
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- Given *k* will be between 1 and *n*! inclusive.
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**Example 1:**
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```c
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Input: n = 3, k = 3
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Output: "213"
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```
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**Example 2:**
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```c
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Input: n = 4, k = 9
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Output: "2314"
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```
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## 题目大意
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给出集合 [1,2,3,…,n]，其所有元素共有 n! 种排列。
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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。
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## 解题思路
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- 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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