Next Permutation

class Solution:
    def nextPermutation(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        def reverse(lo, hi, nums):
            while lo < hi:
                nums[lo], nums[hi] = nums[hi], nums[lo]
                lo += 1
                hi -= 1

        def swap(i, j, nums):
            nums[i], nums[j] = nums[j], nums[i]

        if len(nums) < 2:
            return

        # Find the first minimum from the right
        i = len(nums)-2
        while i >= 0 and nums[i+1] <= nums[i]:
            i -= 1

        # Find the smallest number that is larger than nums[i]
        if i >= 0:
            j = len(nums)-1
            while j >= 0 and nums[j] <= nums[i]:
                j -= 1


            # Swap the elements
            swap(i,j,nums)

            # Reverse elements
        reverse(i+1, len(nums)-1, nums)