class Solution:

    def removeDuplicates(self, nums) -> int:

        for i in range(len(nums)-1,0,-1):#注意要倒序**

            if nums[i]==nums[i-1]:

                del(nums[i])

        return  len(nums)

class Solution:

    def removeDuplicates(self, nums: List[int]) -> int:

        i = 0

        for num in nums:

            if nums[i] != num:

                i += 1

                nums[i] = num

        return len(nums) and i+1