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.

 思路：参考remove duplicates，一样的跳过，不一样的存index。这个就是三次和三次以上的跳过，用map来记录次数即可，想法是一样的。不一样的直接存，一样的判断次数是不是大于二次，大于二次跳过，不是的话就存。

public class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums.length<=2){
            return nums.length;
        }
        Map<Integer,Integer> check=new HashMap<Integer,Integer>();
        check.put(nums[0],1);
        int index=1;
        for(int i=1;i<nums.length;i++){
            if(nums[i]!=nums[i-1]){
                nums[index++]=nums[i];
                check.put(nums[i],1);
            }else{
                if(check.get(nums[i])<2){
                nums[index++]=nums[i];
                check.put(nums[i],check.get(nums[i])+1);
                }
            }
        }
        return index;
    }
}