80. Remove Duplicates From Sorted Array II - Explanation

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        n = len(nums)
        if n <= 2:
            return n
        i = 0
        while i < n - 1:
            if nums[i] == nums[i + 1]:
                j = i + 2
                cnt = 0
                while j < n and nums[i] == nums[j]:
                    j += 1
                    cnt += 1
                for k in range(i + 2, n):
                    if j >= n:
                        break
                    nums[k] = nums[j]
                    j += 1
                n -= cnt
                i += 2
            else:
                i += 1
        return n

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        n = len(nums)
        if n <= 2:
            return n

        count = Counter(nums)
        i = 0
        for num in count:
            nums[i] = num
            count[num] -= 1
            i += 1
            if count[num] >= 1:
                nums[i] = num
                count[num] -= 1
                i += 1
        return i

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        l, r = 0, 0

        while r < len(nums):
            count = 1
            while r + 1 < len(nums) and nums[r] == nums[r + 1]:
                r += 1
                count += 1

            for i in range(min(2, count)):
                nums[l] = nums[r]
                l += 1
            r += 1

        return l

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        l = 0
        for num in nums:
            if l < 2 or num != nums[l - 2]:
                nums[l] = num
                l += 1
        return l