Remove_Duplicates_from_Sorted_Array2.md

080. 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.

Method:

使用pop清除第三个以上的相同元素，该方法会改变数组长度， 故遍历不能用for i in range，而使用while i... i+=1

class Solution(object):
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        count=0
        i=1
        while i<len(nums):
            if nums[i]==nums[i-1]:
                count+=1
            else:
                count=0
            if count>=2:
                nums.pop(i)
                i-=1
            i+=1

也可以不改变数组长度，增设一指针将第三个以上的相同元素赋值为下一不同元素值：

比较时可与前二位比较

class Solution(object):
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        i = 0
        for n in nums:
            if i < 2 or n > nums[i-2]:
                nums[i] = n
                i += 1
        return i