Two Pointers on array
Last updated: May 26, 2026
Quick Overview
Given a sorted array of integers, implement the two-pointer technique to find all unique triplets that sum up to a given target value. Your function should return a list of lists, where each inner list contains three integers that form a valid triplet. Ensure that the output does not contain duplicate triplets and has a time complexity of O(n^2).
Splunk
May 26, 20266
13
1,768 solved
Given a sorted array of integers, implement the two-pointer technique to find all unique triplets that sum up to a given target value. Your function should return a list of lists, where each inner list contains three integers that form a valid triplet. Ensure that the output does not contain duplicate triplets and has a time complexity of O(n^2).
This coding problem is frequently asked during Onsite at Splunk. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Splunk expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find all unique triplets in a sorted array that sum up to a given target value. The two-pointer technique is optimal here because the array is sorted, allowing us to efficie...
Approach
- Initialize: Start by defining a result list to store the unique triplets.
- Iterate: Loop through the array with an index
ifrom 0 tolen(nums) - 3(to ensure space for two more numbe...
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