1. How I sloved

    Repeated numbers had to be moved backward from the list. When checking the numbers in the list, they were added to it if the numbers were not in ‘num_dict’. And the number was moved to the n-th on the list. The number of non-repeated numbers was then returned.

2. Code

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        num_dict = {}
        cnt = 0
        for i,e in enumerate(nums):
            if e not in num_dict.keys():
                num_dict[e] = i
                nums[cnt] = e
                cnt += 1
        return cnt

3. Result

        Runtime : 68 ms(99.07%), Memory usage : 16.5 MB(92.65%)
        (Runtime can be different by a system even if it is a same code.)

Check out the my GitHub repo for more info on the code. If you have questions, you can leave a reply on this post.