[Leetcode]@python 80. Remove Duplicates from Sorted Array II

题目链接

https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/

题目原文

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.

题目大意

给定一个排好序的数组。修改这个数组使得每个数最多可以出现两次。返回去掉多余重复数组后的长度，当然将多余重复数放到数组后面并不影响。

解题思路

(借鉴)使用两个指针prev和curr，判断A[curr]是否和A[prev]、A[prev-1]相等，如果相等curr指针继续向后遍历，直到不相等时，将curr指针指向的值赋值给A[prev+1]，这样多余的数就都被交换到后面去了。最后prev+1值就是数组的长度

代码

class Solution(object):
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums) <= 2:
            return len(nums)
        prev = 1
        curr = 2
        while curr < len(nums):
            if nums[curr] == nums[prev] and nums[curr] == nums[prev - 1]:
                curr += 1
            else:
                prev += 1
                nums[prev] = nums[curr]
                curr += 1
        return prev + 1