Follow up for "Remove Duplicates": What if duplicates are allowed at mosttwice?
For example,
Given sorted arraynums=[1,1,1,2,2,3],
Your function should return length =5, with the first five elements ofnumsbeing1,1,2,2and3. It doesn't matter what you leave beyond the new length.
不要想着把数原封不动的颠倒顺序， 只要在返回长度范围内的数组是对的， 后面的值无所谓
