31. Next Permutation

class Solution:
    def nextPermutation(self, nums):
        """
        :type nums: List[int]
        :rtype: void Do not return anything, modify nums in-place instead.
        """
        if nums == sorted(nums, reverse = True):
            nums.sort()
        else:
            self.exchange(nums)
        return nums

    def exchange(self, nums):
        start_point = len(nums) - 1
        found = False
        while not found and start_point >= 1:
            if nums[start_point] > nums[start_point - 1]:
                found = True
            else:
                start_point -= 1
        position = start_point - 1
        change_part = sorted(nums[position:])
        for i in range(len(change_part)):
            if change_part[i] > nums[position]:
                nums[position] = change_part[i]
                change_part.pop(i)
                break
        position += 1
        # print(nums)
        if len(change_part) >= 1:
            for i in range(len(change_part)):
                nums[position] = change_part[i]
                position += 1
        

instance = Solution()
print(instance.nextPermutation([3, 2, 1]))