How do you solve Remove Duplicates from Sorted Array on LeetCode?

Remove Duplicates from Sorted Array (LeetCode #26) can be solved using Brute Force or Optimal Solution (Two Pointers). The optimal approach is Optimal Solution (Two Pointers) with O(n) time complexity and O(1) space complexity. Key insight: The sorted nature of the array allows us to use a two-pointer technique effectively, as duplicates will always be adjacent.

What is the time complexity of Remove Duplicates from Sorted Array?

The optimal solution for Remove Duplicates from Sorted Array runs in O(n) time and uses O(1) space. This complexity is linear because we make a single pass through the array, updating it in place without needing extra space.

What is the brute force solution for Remove Duplicates from Sorted Array?

The brute force approach for Remove Duplicates from Sorted Array is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach involves creating a new array to store unique elements by checking each element against all others. This is straightforward but inefficient for larger arrays. The optimal Optimal Solution (Two Pointers) approach improves this to O(n).

What algorithm or data structure is used to solve Remove Duplicates from Sorted Array?

Remove Duplicates from Sorted Array uses the following concepts: Array, Two Pointers. The recommended patterns to study are: Hash Map, Array, Two Pointers.

What are the interview tips for Remove Duplicates from Sorted Array?

When you first see this problem, mention the sorted property of the array and how it can simplify finding duplicates. Communicate your thought process clearly, especially when deciding to use the two-pointer technique. Be sure to mention edge cases like an empty array or an array with all identical elements to show you're thinking critically.

What are common mistakes when solving Remove Duplicates from Sorted Array?

Students often forget to handle edge cases, such as an empty array or an array with only one element. Some may attempt to use a more complex data structure unnecessarily, leading to inefficient solutions.

#26

Remove Duplicates from Sorted Array

Easy

ArrayTwo PointersHash MapArrayTwo Pointers

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution (Two Pointers)★
Time	O(n²)	O(n)
Space	O(1)	O(1)

💡

Intuition

Time O(n)Space O(1)

The optimal approach uses two pointers to track the position of unique elements and the current element being examined. This allows us to efficiently overwrite duplicates in the original array without using extra space.

⚙️

Algorithm

3 steps

1Step 1: Initialize a pointer `k` to 1 (the position for the next unique element).
2Step 2: Iterate through the array starting from the second element.
3Step 3: If the current element is different from the previous one, assign it to the position `k` and increment `k`.

solution.py11 lines

1# Full working Python code with comments
2
3def removeDuplicates(nums):
4    if not nums:
5        return 0
6    k = 1  # Pointer for the next unique element
7    for i in range(1, len(nums)):
8        if nums[i] != nums[i - 1]:
9            nums[k] = nums[i]  # Update position k with unique element
10            k += 1  # Move to next position
11    return k

ℹ

Complexity note: This complexity is linear because we make a single pass through the array, updating it in place without needing extra space.

1The sorted nature of the array allows us to use a two-pointer technique effectively, as duplicates will always be adjacent.
2In-place modification is crucial to meet the problem's constraints, which means we should avoid using additional data structures.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.