def removeDuplicates(self, nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    diff_length = 0
    index = -1
    for index, item in enumerate(nums):
        if nums[diff_length] != item:
            diff_length += 1
            nums[diff_length] = item

    if index >= diff_length:
        return diff_length + 1
    else:
        return diff_length