Leetcode.80 | Remove Duplicates from Sorted Array II

Leetcode.80 | Remove Duplicates from Sorted Array II

Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most twice and return 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.

Example 1:

Given nums = [1,1,1,2,2,3],

Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3 respectively.

It doesn't matter what you leave beyond the returned length.

Example 2:

Given nums = [0,0,1,1,1,1,2,3,3],

Your function should return length = 7, with the first seven elements of nums being modified to 0, 0, 1, 1, 2, 3 and 3 respectively.

It doesn't matter what values are set beyond the returned length.

Solution

class Solution:
    
    def removeDuplicates(self, nums: List[int]) -> int:
        n = len(nums)
        if 0 <= n <=2:
            return n
        return self._removeDuplicates_k(nums,2,n)
    
    def _removeDuplicates_k(self,nums:List[int],k:int,n:int) -> int:
            #return [0,start)
        start = 0
        for i in range(n): 
            # 循环遍历，每次只找临界重复数字应该插入的位置
            # nums[start-k] != nums[i] -> 检验插入nums[i]后是否满足条件：
            # 不满足就不插入，满足才更新插入
            if start < k or nums[start-k] != nums[i]:
                nums[start] = nums[i]
                start += 1 
        return start