83. Remove Duplicates from Sorted Array

🟩 Easy

Question

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.

Two Pointer Approach

Two Pointers: i for distinct element, k for searching.

If nums[k] is duplicate, put in i+1(since k goes faster than i, so k > i). Therefore, nums[0... i] are the distinct elements in original array.

Complexity

• Time complexity: O(n)

• Space complexity: O(1)

Code

def removeDuplicates(self, nums):
    """
    :type nums: List[int]
    :rtype: int
    """
    i, k = 0, 1
    while (k < len(nums)):
        if nums[k] != nums[i]:
            nums[i+1] = nums[k]
            i += 1
        k += 1
    return i+1