Remove Duplicates from Sorted Array II问题及解法

问题描述：

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

示例：
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.

问题分析：

在原有空间内，设置双指针，一个指向变化后的数组，一个指向现有数组，遇到重复值达三个的，删掉其中一个。

过程详见代码：

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