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.

Solution：Two pointers

思路：nums[new_i - 2] != nums[i] 则可加
Time Complexity: O(N) Space Complexity: O(1)

Solution Code：

class Solution {
    public int removeDuplicates(int[] nums) {
        int new_i = 0;
        for(int i = 0; i < nums.length; i++) {
            if(new_i < 2 || nums[new_i - 2] != nums[i]) {
                nums[new_i++]= nums[i];
            }
        }
        return new_i;
    }
}