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]]

BackTracking

回溯法:

  1. 修改当前值
  2. 递归current node
  3. 还原当前值
def permute(self, nums):
“””
:type nums: List[int]
:rtype: List[List[int]]
“””

def backTrack(nums, level):
if level == len(nums)-1:
self.ans.append(list(nums))
return
for i in range(level, len(nums)):
nums[level], nums[i] = nums[i], nums[level]
backTrack(nums, level+1)
nums[level], nums[i] = nums[i], nums[level]
self.ans = []
backTrack(nums, 0)
return self.ans