【python3】leetcode 26. Remove Duplicates from Sorted Array（easy）

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26. Remove Duplicates from Sorted Array（easy）

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

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

Example 1:
Given nums = [1,1,2],

Your function should return length = 2, with the first two elements ofnums being1and 2
respectively.
It doesn't matter what you leave beyond the returned length.
Example 2:
Given nums = [0,0,1,1,1,2,2,3,3,4],

Your function should return length = 5, with the first five elements of numsbeing modified to 0,1,2,3,and 4 respectively.
It doesn't matter what values are set beyond the returned length.

题意：问有几个不重复的数字假设k个，返回k且这几个不重复的数字必须在nums的前 k个（inplace）

1 my solution ：直接遍历删除重复数字，最后返回数组长度

class Solution:
    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums) == 0 or len(nums) == 1: return len(nums) 
        i = 1
        while(i < len(nums)):
            if nums[i] == nums[i-1]:del nums[i]
            else:i += 1
        return len(nums)

2 two pointer

看example一直强调只要前面k个是满足条件的数字即可，就是说nums[k:] 是啥都无所谓

所以直接遍历修改前k个数字

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