80. Remove Duplicates from Sorted Array II 解题记录

题目描述：

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.

解题思路：

因为是已经排序好的数组，所以只要将当前的元素与上一个元素比较是否相等，再用一个数记录个数就可以了。

代码：

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        if(nums.size() <= 2)
            return nums.size();
        int DupNum = 1;
        for(int i = 1; i < nums.size(); i++){
            if(nums[i] != nums[i-1])
                DupNum = 1;
            else{
                DupNum++;
                if(DupNum > 2)
                    nums.erase(nums.begin()+(i--));
            }
        }
        return nums.size();
    }
};