Master Coding Interview Preparation in 2025 with These 15 Patterns
Forget LeetCode learn these 15 coding interview patterns
If you have prepared for coding interviews, you know how daunting they can be. In addition to your regular work, you need to spend considerable time practicing data structures and algorithms just for the interview.
I have done that but more often than not it’s either miss or hit. If you get the coding problem you have practiced then the interview can be a breeze, all you need to do is act as if you are solving that question first time but if you get a really unknown question then good luck to you.
I knew that the method was not full proof and needed improvement and when I solved so many problems I noticed certain tricks which can help you to solve many problems, for example, the two pointer approach on linked list can be used to find the middle element as well as to detect any cycle.
I didn’t know that these are essential coding patterns until I came across Grokking the Coding Interview Patterns course from Educative. This course teaches you 24 coding patterns which can be used to solve thousands of Leetcode problems.
That’s the first time I came across this terminology and also learned many other patterns which I didn’t even know. Just knowing that, helped me a lot in my coding interview prep and also to many of my readers who thanked and appreciated me that I told them about these patterns and this course.
In this article, I am going to share 15 such coding patterns which can be used to solve 100+ coding problems. Many of them are also covered in Grokking the Coding Interview Pattern course on Educative, in greater depth.
Now, you don’t need to blindly solve many coding problems just to get your hands on it. Instead you learn these patterns and then start solving coding problems where you can use these patterns.
To make your preparation structured and effective, I highly recommend you to join a platform like Algomonster or a course like Grokking the Coding Interview Patterns from Educative.
Grokking the Coding Interview Patterns – AI-Powered Course
This course covers all key patterns you need for interviews and integrates interactive practice. Additionally, Educative’s AI powered Personalized Interview Preparation Plan is a great resource to tailor your learning to your pace and goals.
Tech Interview Prep: Get Hired
Without any further ado, here are the 15 essential coding patterns you should master, along with 2–3 LeetCode problems to practice for each.
1. Two Pointers
Two Pointers is a versatile pattern that involves using two pointers to traverse an array or linked list efficiently.
This was the first coding pattern I learned and it works remarkably well on solving linked list and array based problems like finding the middle elements of the list or finding the kth element from the end of the list.
Key Concepts:
- Optimize problems involving pairs, such as sum or difference.
- Avoid nested loops to reduce time complexity.
LeetCode Problems:
- Two Sum II — Input Array Is Sorted (167)
- Remove Duplicates from Sorted Array (26)
- Move Zeroes (283)
2. Prefix Sum
Prefix Sum is a powerful technique for optimizing range queries in arrays. By preprocessing cumulative sums, you can solve range-based problems efficiently. This coding pattern is also very important for solving array based problems like Subarray Sum Equals K on Leetcode.
Key Concepts:
- Precompute cumulative sums for quick access.
- Use for range queries like subarray sums.
LeetCode Problems:
- Range Sum Query — Immutable (303)
- Subarray Sum Equals K (560)
- Minimum Value to Get Positive Step by Step Sum (1413)
3. Sliding Window
Sliding Window is a powerful pattern to optimize problems involving contiguous subarrays. This problem can be tough to understand at first but once you solve a couple of problems, you will appreciate the simplicity of it.
Key Concepts:
- Maintain a window over part of the array.
- Expand or contract the window as needed.
LeetCode Problems:
- Longest Substring Without Repeating Characters (3)
- Maximum Sum of Subarray of Size K (643)
- Minimum Window Substring (76)
4. Fast & Slow Pointers
Fast & Slow Pointers (also called the Floyd’s Cycle Detection) are commonly used for cycle detection in Linked Lists.
Key Concepts:
- Use two pointers moving at different speeds.
- Detect cycles or meeting points in a sequence.
LeetCode Problems:
- Linked List Cycle (141)
- Find the Duplicate Number (287)
- Happy Number (202)
5. LinkedList In-Place Reversal
This pattern focuses on reversing portions of a Linked List without extra space. In place algorithms can be used when you have memory constraint.
Key Concepts:
- Reverse a Linked List iteratively or recursively.
- Solve problems requiring sublist reversal.
LeetCode Problems:
- Reverse Linked List (206)
- Reverse Linked List II (92)
- Swap Nodes in Pairs (24)
6. Monotonic Stack
The Monotonic Stack is a structured stack that maintains elements in sorted order (increasing or decreasing).
Key Concepts:
- Solve problems involving the next greater or smaller element.
LeetCode Problems:
- Daily Temperatures (739)
- Next Greater Element I (496)
- Largest Rectangle in Histogram (84)
7. Top ‘K’ Elements
This pattern focuses on efficiently finding the top K largest, smallest, or most frequent elements. You can use this pattern to solve problems like how to find the Kth largest element in a given array.
You can also find many questions based on these patterns on Educative-99 , where you will get a chance to solve 99 selected questions instead of 2800 Leetcode problems.
Key Concepts:
- Use heaps (priority queues) or sorting.
LeetCode Problems:
- Top K Frequent Elements (347)
- Kth Largest Element in an Array (215)
- Find K Pairs with Smallest Sums (373)
8. Overlapping Intervals
This pattern involves merging or handling overlapping intervals in sorted order.
Key Concepts:
- Sort intervals and merge based on conditions.
LeetCode Problems:
- Merge Intervals (56)
- Insert Interval (57)
- Meeting Rooms II (253)
9. Modified Binary Search
Modified Binary Search optimizes searching in sorted or rotated arrays.
Key Concepts:
- Apply binary search creatively for custom conditions.
LeetCode Problems:
- Binary Search (704)
- Search in Rotated Sorted Array (33)
- Find Peak Element (162)
10. Binary Tree Traversal
This is not a pattern but an essential binary tree concept which is presented as a pattern. Basically you need to learn various traversal techniques such as in-order, pre-order, and post-order to solve tree problems.
Another key thing to remember is that with the in-order traversal you can print the list in a sorted order. Not many developers know this but it’s a very good thing to remember.
LeetCode Problems:
- Binary Tree Inorder Traversal (94)
- Maximum Depth of Binary Tree (104)
11. Depth-First Search (DFS)
DFS explores tree or graph nodes as deep as possible before backtracking. In other words, all the nodes in one branch are explored before starting another branch.
LeetCode Problems:
- Path Sum (112)
- Number of Islands (200)
12. Breadth-First Search (BFS)
BFS explores nodes level by level, often implemented with a queue.
LeetCode Problems:
- Binary Tree Level Order Traversal (102)
13. Matrix Traversal
Matrix Traversal involves navigating through 2D grids or matrices.
LeetCode Problems:
- Flood Fill (733)
14. Backtracking
Backtracking solves problems recursively by trying all solutions and backtracking when needed.
LeetCode Problems:
- Subset (78)
15. Dynamic Programming Patterns
Dynamic Programming focuses on breaking problems into subproblems and solving them optimally. I also suggest you to go through Grokking Dynamic Programming Patterns for Coding Interviews on Educative to better understand these Dynamic programming patterns.
LeetCode Problems:
- Climbing Stairs (70)
- Longest Increasing Subsequence (300)
That’s all about 15 essential Coding Interview Patterns for interviews. You must master these 15 patterns if you want to crack the interview and get the offer you want. I also encourage you to check out Grokking the Coding Interview Patterns on Educative for interactive, in-depth explanations and real coding exercises.
Grokking the Coding Interview Patterns – AI-Powered Course
You will also learn 24 patterns there and then you can combine these patterns with consistent LeetCode practice, and you’ll be well-prepared to land your dream job!
Preparing for coding interviews can be daunting, but focusing on essential problem-solving and coding patterns can make it significantly easier. Instead of learning solutions to individual problems, mastering these patterns will help you tackle various coding challenges effectively.
You can also start with Educative-99 , where you will get a chance to solve 99 selected questions instead of 2800 Leetcode problems. This will also help you to master the above coding patterns better.
Educative-99 in Python: Accelerate Your Coding Interview Prep – AI-Powered Learning for Developers
Hopefully, this should be a good starting point for you.
P. S. — If you want to do just one thing, join AlgoMonster and start practicing coding patterns suggested by FAANG expert and ex Google Engineers. This is the quickest and best way to prepare for interviews.
And here is a nice diagram to remember these patterns
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