Leetcode解题-去除有序数组中的重复元素

描述

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

For example,
Given input array nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn’t matter what you leave beyond the new length.

给定一个排序后的数组，要求移除重复的元素，返回新的数组长度。要求O(1)空间

分析

这是一道简单题，使用两指针，一个记录去重后数组的尾部，一个扫原数组。可以实现inplace的时间O(n)空间O(1)的算法。另外，理解原题后就会发现，其实“有序”这个限定过于严格，只要保证相同的元素排列在一起就可以使用该算法。比如：[6, 6, 8, 8, 8, 7]

代码

Python

class Solution:
    def removeDuplicates(self, nums):
        if not nums:
            return 0
        i = 1
        for n in nums[1:]:
            if n != nums[i - 1]:
                nums[i] = n
                i += 1
        return i