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Permutations

Problem Statement​

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

Leetcode Link

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.

Code​

Python
class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:

        def backtrack(d,visited,ans,nums):
            if len(d)==len(nums):
                ans.append(d.copy())
                return

            for i in range(len(nums)):
                if not visited[i]:
                    d.append(nums[i])
                    visited[i] = True
                    backtrack(d,visited,ans,nums)
                    d.pop()
                    visited[i] = False

        visited = [0]*len(nums)
        d,ans = [],[]
        backtrack(d,visited,ans,nums)
        return ans