全排列

Permutations

个人笔记

问题：全排列

考察：数组、回溯

来源：DSA Prep / Citadel

链接：https://leetcode.com/problems/permutations

Problem: Permutations

Patterns: Array, Backtracking

Recency: 2yr

Link: https://leetcode.com/problems/permutations

Source: https://www.dsaprep.dev/blog/citadel-coding-interview-questions/

解析

思路：回溯构造排列，用 used 数组标记哪些数字已被选择。路径长度达到 n 时记录一个排列。

复杂度：时间 O(n! * n)，空间 O(n) 不计输出。

Approach: Use backtracking with a `used` array. At each depth choose one unused number, append it, recurse, and then undo the choice.

Complexity: Time $O(n\cdot n!)$ , space $O(n)$ excluding output.