Permutations

Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
Input: nums = [0,1]
Output: [[0,1],[1,0]]
Input: nums = [1]
Output: [[1]]
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

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