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.

解题思路：

设置index＝2， 遍历数组，与index－2对比，找到不同的数字就赋值，index++，最后返回index。

class Solution {
public:
int removeDuplicates(vector<int>& nums) {
if (nums.size() < 2) return nums.size();

int index = 2;
for (int i = 2; i < nums.size(); i++) {
if (nums[i] != nums[index - 2]) {
nums[index++] = nums[i];
}
}

return index;
}
};