80. Remove Duplicates from Sorted Array II.md

80. Remove Duplicates from Sorted Array II (Medium)

[tag] two pointer.
It's a bit tricky.

• use two pointers one fixed pointer(l) and one floating(r)
• numbers on left of l is in order.
• r will stay unless r found a different value

'''
    l 
1,1,2,2,2,2,2,2,3,2,3,4
    r
'''
class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        l, r = 2, 2
        while r < len(nums):
            if nums[l-2] != nums[r]:
                nums[l] = nums[r]
                l += 1
            r += 1
        return l