# [80\. Remove Duplicates from Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/)

:::spoiler Hint

class Solution {
public:
    int removeDuplicates(vector<int>& nums)
    {
        // Initialize the index to insert the next valid element
        // Initialize the count of the current element to 1 (the first element is always counted once)

        // Iterate through the array starting from the second element
        for ()
        {
            // If the current element is the same as the previous element, increment the count
            if ()
            {
            }
            else // If the current element is different from the previous element, reset the count to 1
            {
            }
            
            // If the count is less than or equal to 2, we can keep this element
            if ()
            {
                // Place the current element at the insertIndex and increment insertIndex
            }
        }
        // Return the index where the next element would be inserted, which is the new length of the array
    }
};

:::

:::spoiler Solution

class Solution {
public:
    int removeDuplicates(vector<int>& nums)
    {
        int insertIndex = 1;
        int cnt = 1;

        for (int i = 1; i < nums.size(); ++i)
        {
            if (nums[i] == nums[i - 1]) ++cnt;
            else cnt = 1;
            if (cnt <= 2) nums[insertIndex++] = nums[i];
        }
        return insertIndex;
    }
};

- 時間複雜度：$O(N)$
- 空間複雜度：$O(1)$
:::