26. Remove Duplicates from Sorted Array - python3

Given a sorted array nums, remove the duplicates in-place such that each element appears only once and returns the new length.

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

Clarification:

Confused why the returned value is an integer but your answer is an array?

Note that the input array is passed in by reference, which means a modification to the input array will be known to the caller as well.

Internally you can think of this:

// nums is passed in by reference. (i.e., without making a copy)
int len = removeDuplicates(nums);

// any modification to nums in your function would be known by the caller.
// using the length returned by your function, it prints the first len elements.
for (int i = 0; i < len; i++) {
    print(nums[i]);
}

My Answer 1: Wrong Answer

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        result = []
        for i in nums:
            if i not in result:
                result.append(i)
        return len(result)

왜 안되는지 모르겟음
추가 메모리를 사용해서....?

그냥 중복 제거한 리스트만 존재하면 된다고 생각했는데... 이상;

My Answer 2: Accepted (Runtime: 76 ms / Memory Usage: 16.1 MB)

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        i=0
        for j in range(1,len(nums)):
            if nums[j]!=nums[j-1]:
                i+=1
                nums[i]=nums[j]
        return i+1

추가 메모리 없이 nums 로만 비교
중복아닌 것들을 앞으로 땡기고 그 길이를 의미하는 i+1 을 리턴