000046-Permutations

Problem

https://leetcode.com/problems/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

backtracking

class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        res = []
        def backtrack(nums, path=[]):
            if len(path) == len(nums):
                res.append(path[:])
                return
            for num in nums:
                if num in path:
                    continue
                path.append(num)
                backtrack(nums, path)
                path.pop() # backtrack
        backtrack(nums, [])

        return res