Permutations

1def permute(nums: List[int]) -> List[List[int]]:
2    res = []
3    used = [False] * len(nums)
4    cur = []
5    
6    def dfs() -> None:
7        if len(cur) == len(nums):
8            res.append(cur[:])
9            return
10        for i in range(len(nums)):
11            if used[i]:
12                continue
13            used[i] = True
14            cur.append(nums[i])
15            dfs()
16            cur.pop()
17            used[i] = False
18    
19    dfs()
20    return res