[算法题] Remove Duplicates from Sorted Array ii

题目内容

本题来源LeetCode

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.

 题目思路

本题难度：medium

这个题目的思路就是经典的快慢指针方法。假如nums的长度小于等于2，则直接返回nums数组。然后设立两个指针i,index。初始化都指向第3个元素，快指针为i，慢指针为index。假如nums[i]！=nums[index-2]，则慢指针加一。

Python代码

class Solution(object):
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        l=len(nums)
        if l<=2:
            return l
        index=2
        for i in range(2,l):
            if nums[i]!=nums[index-2]:
                nums[index]=nums[i]
                index+=1
        return index