Key Coding Patterns to Master

I failed 30+ coding interviews until I understood and applied these concepts.  I’ve applied and interviewed at every MAANG company as well as countless startups across Malaysia, India and the USA. I’ve had many rejections but each has taught me something great about how tech hiring works.  Here’s what I wish someone had told me earlier: Let me break it down for you 👇 1️⃣ Arrays & Patterns → Learn how to move pointers with intention:   Two Pointers, Sliding Window, Prefix Sums.  → Add Binary Search + Sorting, and you can solve 30% of Leetcode. 2️⃣ Recursion & Decision Trees → If you're scared of recursion, you haven’t seen it as a decision tree. This one shift helped me unlock: ✅ Backtracking   ✅ Binary Tree Traversals   ✅ DP States   ✅ Even Subset & Combination problems  See the tree. Build the logic. Code will follow. 3️⃣ Graphs → 90% of graph questions are DFS or BFS.   → The real twist? Whether it’s on a matrix or an adjacency list.  Master:   ✅ Cycle Detection   ✅ Shortest Path   ✅ Connected Components Graphs only feel scary when you don’t code them enough. 4️⃣ HashMaps The hidden hero of 100+ problems. → Use for frequencies, fast lookups, and avoiding O(N²) traps.   → Ask yourself in slow problems: “Can I precompute with a HashMap?” Interviewers LOVE clean hashmap tricks.   Show them, don’t just tell them. 5️⃣ Heaps → Top K problems? Min-Heap.   → Frequent Elements? Max-Heap.   → Sliding Window Median? You’ll need two heaps. 6️⃣ Dynamic Programming Yes, it's hard.   But no, you don’t need to do 100+ DP problems. Start with: ✅ LCS   ✅ 0/1 Knapsack   ✅ LIS   ✅ Partition Equal Subset  Master 1D → 2D transitions and memo → tabulation.   That’s 90% of the game. You don’t need quantity, you need clarity. → 80 solid problems solved deeply > 300 solved mindlessly   → Debug out loud, talk through your approach, focus on patterns And above all? Don’t let rejection stop you. Let it refine you. You've got this    If you’re in the grind right now, I see you. You're closer than you think.

Mohammad F. has taught DSA to 2000+ students, and the biggest lesson? You don’t need to solve hundreds of problems. You just need to master these 8 patterns that cover 80% of all Leetcode problems. Here’s your roadmap 👇 1. Sliding Window = When you need to find subarrays or substrings in a linear DS (like arrays or strings) that meet a certain condition _ Used in problems like: longest subarray, max sum of k-length window, etc. 2. Two Pointers = For sorted arrays/strings where you move 2 pointers to meet a condition _ Used in: pair sums, palindrome checks, merging sorted arrays 3. Modified Binary Search = Classic binary search but adapted for rotated arrays, infinite search space, or conditions beyond equality _ Used in: search in rotated array, peak element, kth element in sorted matrix 4. Subset/Backtracking = When you need to generate all combinations or permutations _ Used in: subsets, combinations, permutations, N-Queens 5. Top-K Elements = When you need to find the k smallest/largest items efficiently _ Always think heaps/priority queues here 6. DFS/BFS on Trees = To explore all nodes in a tree—depth-first (recursion) or level-by-level (queues) _ Used in: max depth, level order traversal, path sums 7. Topological Sort = Used in Directed Acyclic Graphs when there's dependency (prerequisite) between nodes _ Common in: course scheduling, task ordering 8. Dynamic Programming = The final boss. For overlapping subproblems with optimal substructure _ Used in: knapsack, DP on strings, grid paths, longest subsequences Save this post. Don’t chase problem counts. Master patterns → practice problems within each → build real intuition. Here is the DSA Sheet, go and start learning: https://lnkd.in/ggZVrwfs

What I learned after solving 600+ LeetCode problems (300+ hours of efforts) (This will help you nail 80-90% of your coding interviews, if you do it right) During my Bachelor days at BITS Pilani, I solved 600-700+ LeetCode problems to prepare for coding interviews. At first, it felt like a grind, just something I had to do to land a job.  But looking back, those hundreds of hours weren’t just about interviews, they shaped the way I think, debug, and approach complex problems.  Even now, when switching teams or tackling a new domain, the problem-solving muscle I built through LeetCode still pays off.  If you're preparing for coding interviews, here’s what I wish someone told me before I started 👇  1️⃣ The Order You Solve Problems In Matters More Than You Think A huge mistake? Jumping straight into graphs and dynamic programming before mastering the basics.  🔹 First, nail the fundamentals: Arrays, Strings, HashMaps, Linked Lists, Trees, Binary Search.   🔹 Then, go deeper: Recursion, Backtracking, Sliding Window, BFS/DFS.   🔹 Finally, tackle the hardest ones: Dynamic Programming, Graphs, Tries, Bit Manipulation.  Solving problems in a structured order will save you months of frustration.  2️⃣ Quality Over Quantity, Memorizing Solutions Won’t Get You Hired I see people bragging about solving 1,000+ problems, but here’s the truth:  150 well-understood problems >>> 500 brute-force attempts  🔹 The goal isn’t to memorize solutions but to recognize patterns.   🔹 Every medium/hard problem is just a remix of a classic pattern.   🔹 If you can’t explain why a solution works, you haven’t understood it.  I’d rather fully understand 150 problems than struggle through 500 and still freeze in an interview.  3️⃣ Patterns Are Everything, Learn Them, and You’ll Never Be Stuck LeetCode isn’t about learning 600 different solutions. It’s about seeing the same 20-30 ideas appear again and again.  Here’s how I break it down:  🔹 Medium problems → Identify the right pattern (Binary Search, Two Pointers, Sliding Window, BFS, DP).   🔹 Hard problems → Usually have a single trick—once you spot it, 80% of the work is done.  If you’ve seen House Robber 1, you’ll immediately understand House Robber 2 and Paint Fence. If you’ve solved Merge Intervals, you’ll recognize the same concept in Meeting Rooms, Insert Interval, and Skyline Problem.  You don’t need to learn new ideas for every problem. You just need to recognize the remix.  Continued Here (I’ve spent good time on this, read it once) : https://lnkd.in/gjCCdYe5

𝐓𝐫𝐲 𝐭𝐡𝐢𝐬 𝐡𝐚𝐜𝐤 𝐭𝐨 𝐚𝐜𝐞 𝐲𝐨𝐮𝐫 𝐜𝐨𝐝𝐢𝐧𝐠 𝐢𝐧𝐭𝐞𝐫𝐯𝐢𝐞𝐰 𝐩𝐫𝐞𝐩𝐚𝐫𝐚𝐭𝐢𝐨𝐧. LeetCode has around 3K problems. With this huge set of problems, the biggest challenge is where to start or what to focus on. I have helped many engineers to prepare for their interviews. After talking to many developers who recently went through interviews and keeping the LeetCode problems distribution in mind, I came up with the top 7 coding patterns with the highest ROI. To prepare smartly, you should not ignore these patterns. Here is the list: 💠Two Pointers 💠Sliding Window 💠Depth-First Search & Breadth-First Search 💠Binary Search 💠Interval Merge 💠Recursion/Backtracking Each pattern offers a strategic approach for understanding and solving a wide array of coding problems. These patterns are the keystones that will enable you to recognize problem types and apply familiar solutions, saving you precious time and mental energy during high-stakes interviews. Ref: 𝐆𝐫𝐨𝐤𝐤𝐢𝐧𝐠 𝐭𝐡𝐞 𝐂𝐨𝐝𝐢𝐧𝐠 𝐈𝐧𝐭𝐞𝐫𝐯𝐢𝐞𝐰 - https://lnkd.in/g6ApdjVW