leetcode - 46. Permutations

Description

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]
Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]
Output: [[1]]

Constraints:

1 <= nums.length <= 6
-10 <= nums[i] <= 10
All the integers of nums are unique.

Solution

Iterate, the core function is f = each_num + f(remaining_nums)

Time complexity: $o(n!)$
Space complexity: $o(n)$

Code

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        if len(nums) == 1:
            return [nums]
        res = []
        for index, item in enumerate(nums):
            next_permutation = self.permute(nums[:index] + nums[index + 1:])
            res += [[item] + np for np in next_permutation]
        return res