Skip to content

46. Permutations

Difficulty Topics

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

permutations.py
class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        n = len(nums)
        res = []

        def go(curr, seen):
            nonlocal res

            if len(curr) == n:
                res.append(curr[:])
                return

            for i, x in enumerate(nums):
                if i in seen: continue
                seen.add(i)
                curr.append(x)
                go(curr, seen)
                seen.remove(i)
                curr.pop()

        go([], set())
        return res