leetcode26 Remove Duplicates from Sorted Array

"""
Given a sorted array nums, 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 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 of nums being 1 and 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 nums being modified to 0, 1, 2, 3, and 4 respectively.
It doesn't matter what values are set beyond the returned length.
"""
"""
本题的关键是不用新开辟数组
而是用一个指针来在原数组上存放结果
"""

class Solution:
    def removeDuplicates(self, nums):
        if not nums:
            return 0
        j = 0 #用来借用原数组上的空间存答案数组的指针
        for i in range(1, len(nums)):
            if nums[i] != nums[i-1]:
                j += 1
                nums[j] = nums[i]
        return j+1