Remove Duplicates from Sorted Array
Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once.
The relative order of the elements should be kept the same.
Return the number of unique elements in nums.
The first k elements of nums should contain the unique elements, where k is the returned value.
Example 1
Input
nums = [1,1,2]
Output
2 [1,2]
Explanation
The unique elements are [1,2].
The first 2 positions of nums should contain:
[1,2]
Example 2
Input
nums = [0,0,1,1,1,2,2,3,3,4]
Output
5 [0,1,2,3,4]
Explanation
The unique elements are:
[0,1,2,3,4]
So k = 5.
Constraints
Hints:
Hint 1
Since the array is already sorted, equal elements will always be next to each other.
Hint 2
Use one pointer to scan the array and another pointer to place each new unique element.
Author & Technical Reviewer
Technically reviewed by: ExamAdda Technical Review Team
Technical Reviewers, ExamAdda
Software engineers at ExamAdda who check every article's definitions, complexity claims and code examples before and after publishing.
Published
Aug 19, 2026
Last updated
Aug 19, 2026
Content Verification Methodology
Definitions and complexity claims were checked against authoritative computer-science references. Code examples were compiled and tested with standard, boundary and edge-case inputs.
Expected Output