LeetCode OJ：Remove Duplicates from Sorted Array II（移除数组中的重复元素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.

 
典型的双指针问题，维护两个指针不断更新就可以了，代码如下：

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int sz = nums.size();
        if(!sz) return 0;
        int start = 0;//第二个指针
        int i = 0;//第一个指针
        int count = 0;
        int key = nums[0];
        for(; i < sz; ++i){
            if(nums[i] == key)
                count++;
            else{
                for(int k = 0; k < min(2, count); ++k)
                    nums[start++] = key;//更改数组元素，指针前移
                key = nums[i];
                count = 1;
            }
        }
        for(int k = 0; k < min(2, count); ++k)
            nums[start++] = key;
        return start;
    }
};