80. Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?

For example,
Given sorted array 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. It doesn't matter what you leave beyond the new length.

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        
        int len = nums.size();
        if(len == 0){
            return 0;
        }
        int start = 0;
        int num = 0;
        for(int i = 1; i < len; i ++){
            if(nums[start] == nums[i]){
                num ++;
                if(num < 2){
                    nums[++start] = nums[i];
                }
            }else{
                num = 0;
                nums[++start] = nums[i];
            }
        }
        return start + 1;
    }
};