class Solution:
    def permute(self, nums: List[int]) -> List[List[int]]:
        def helper(currIndex, currPermutation):
            if len(currPermutation) == len(nums):
                res.append(currPermutation[:])
                return
            if currIndex >= len(nums):
                return

            for i in range(currIndex, len(nums)):
                nums[currIndex], nums[i] = nums[i], nums[currIndex]
                currPermutation.append(nums[currIndex])
                helper(currIndex + 1, currPermutation)
                del currPermutation[-1]
                nums[currIndex], nums[i] = nums[i], nums[currIndex]

        res = []
        helper(0, [])
        return res