Beginner~2h
Two Pointers in Data Structures & AlgorithmsInterview Readiness Check
Eliminate the inner loop — sort and converge from both ends for O(n) solutions to O(n²) problems.
sorted arraypalindromecontainer waterpair sumleft right pointers
Learning path
Try a sample question
Given a sorted array, find if any two numbers sum to a target. Which pattern solves this in O(n) time without extra space?
A.Two pointers — left at start, right at end. If sum < target move left right, if sum > target move right left, stop when they meet.
B.HashMap — store each number, look up target - number
C.Binary search for each element's complement — O(n log n)
D.Sliding window over a fixed-size subarray
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What this module tests
- Conceptual understanding of two pointers fundamentals
- Trade-offs and design decisions in real system scenarios
- sorted array and palindrome — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the Two Pointers check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the Two Pointers check test?
- The check covers eliminate the inner loop — sort and converge from both ends for o(n) solutions to o(n²) problems. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Two Pointers?
- Key concepts include: sorted array, palindrome, container water, pair sum, left right pointers. These frequently appear in data structures & algorithms interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study Two Pointers?
- Most engineers spend around 2 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before Two Pointers?
- Two Pointers builds on Arrays & Hashing. Complete those first for the best results.
- Is sorted array, palindrome, container water covered?
- Yes. The Two Pointers module covers sorted array, palindrome, container water among other key concepts. The check includes questions that reflect real data structures & algorithms interview patterns.