线性表-Remove Duplicates from Sorte

描述
Follow up for ”Remove Duplicates”: What if duplicates are allowed at most twice?
For example, Given sorted array A = [1,1,1,2,2,3],
Your function should return length = 5, and A is now [1,1,2,2,3]
思路：
这道题是上一篇的升级版，允许最多有两个重复的数字，与上一篇思路基本一致，额外一个变量来记录次数，注意index的初值以及判断数值不等时的改变，如果是未排序的数组则需要引入一个hashmap来记录出现的次数。

代码1 python
class Solution:
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums) < 3:
            return len(nums)
        index = 2
        for i in range(len(nums) - 2):
            if nums[index - 2] != nums[i+2]:
                nums[index] = nums[i+2]
                index += 1        
        return index

代码2 c++
class Solution:
public:
    int removeDuplicates(vector <int>& nums){
        if (nums.size() <= 2) return nums.size();
        int index = 2;
        for (int i = 2 ; i < nums.size(); i++){
            if(nums[index - 2] != nums[i])
                nums[index++] = nums[i]; 
        }
        return index;
    }

下面再提供一种思路，自行理解

代码3 c++
class Solution:
public:
    int removeDuplicates(vector <int>& nums){
        int n = nums.size();        
        int index = 0;
        for (int i = 0 ; i < n; ++i){
            if( i >0 && i < n - 1 && nums[i] == nums[i - 1] && nums[i] == nums[i +1])
                continue;
            nums[index++] = nums[i]; 
        }
        return index;
    }