1. 题意

删除有序数组中的重复元素，同一元素不能超过两次。

2. 题解

leetcode26. 删除有序数组中的重复项的升级版本，只需要考虑$nums[len-2]\ne nums[j]$即可，$len$是排列好的有序数组长度，$j$遍历完整个数组。

• 通解$k=2$

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

• 模拟

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