Two Pointers Examples: Solved Problems with Step-by-Step Explanations
Learn the Two Pointers pattern through carefully selected examples. Each example includes problem statement, intuition, code in multiple languages, complexity analysis, and follow-up variations. Use two pointers converging or diverging on sorted arrays or linked lists.
Example 1: Classic Problem (Easy)
Problem: Two Sum II (Sorted Array)
Description: Find two numbers in a sorted array that sum to a target.
Approach: Use two pointers from both ends. If sum < target, move left pointer right. If sum > target, move right pointer left.
Complexity: Time O(n), Space O(1)
Key Insight: This is a classic easy Two Pointers problem. Understanding this example helps you solve 6 similar problems.
Interview Tip: Explain your approach before coding. State the time and space complexity upfront.
Example 2: Interview Favorite (Medium)
Problem: Container With Most Water
Description: Find two lines that together with x-axis form a container holding the most water.
Approach: Start pointers at both ends. Calculate area, then move the shorter line pointer inward.
Complexity: Time O(n), Space O(1)
Key Insight: This is a classic medium Two Pointers problem. Understanding this example helps you solve 6 similar problems.
Interview Tip: Explain your approach before coding. State the time and space complexity upfront.
Example 3: Advanced Application (Hard)
Problem: 3Sum
Description: Find all unique triplets that sum to zero.
Approach: Sort array. Fix one element, use two pointers for the remaining pair. Skip duplicates.
Complexity: Time O(n), Space O(1)
Key Insight: This is a classic hard Two Pointers problem. Understanding this example helps you solve 6 similar problems.
Interview Tip: Explain your approach before coding. State the time and space complexity upfront.
Why These Examples Work
Each example was chosen because it:
Study the pattern, not just the solution. The goal is to recognize when to apply Two Pointers in new, unseen problems.
Pattern Recognition Checklist
Before coding, ask yourself:
If 2+ answers are yes, try the Two Pointers approach.
Categorization & Filters
Frequently Asked Questions
How many Two Pointers examples should I study?
Should I memorize these examples?
What language should I use for Two Pointers?
Practice 18+ Two Pointers problems with instant AI feedback on W Code!
Start Learning Free