Master LeetCode Interview Questions with Practice Problems

🚀 OOP Interview Refresher — Foundations, Pillars & Relationships Object-Oriented Programming is more than syntax—it’s the foundation of scalable software design. This visual summarizes the essentials: 🧱 Core building blocks: Classes & Objects 🛡️ Four pillars: Encapsulation, Abstraction, Inheritance, Polymorphism 🔗 Relationships: Association, Aggregation, Composition, Dependency ⚙️ Lifecycle methods: __construct() and __destruct() 👉 A strong grasp of these concepts makes system design, frameworks, and interviews much easier. Clear concepts. Better architecture. Stronger engineering fundamentals. #OOP #SoftwareEngineering #Programming #SystemDesign #CodingInterview

𝗗𝗦𝗔 𝗧𝗼𝗽𝗶𝗰-𝗪𝗶𝘀𝗲 𝗟𝗲𝗲𝘁𝗖𝗼𝗱𝗲 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀 — 𝗦𝗺𝗮𝗿𝘁 𝗪𝗮𝘆 𝘁𝗼 𝗠𝗮𝘀𝘁𝗲𝗿 𝗣𝗿𝗼𝗯𝗹𝗲𝗺 𝗦𝗼𝗹𝘃𝗶𝗻𝗴! Preparing for coding interviews? Practicing LeetCode questions topic-wise is one of the most effective ways to build strong Data Structures and Algorithms (DSA) fundamentals. It helps you understand patterns, improve logic, and solve problems faster with confidence. Start with arrays and strings, then move to linked lists, stacks, queues, trees, graphs, recursion, and dynamic programming. Focus on problem-solving techniques like sliding window, two pointers, binary search, greedy algorithms, and backtracking. Consistent practice with a structured approach will boost your coding skills and help you crack technical interviews at top companies. Practice smart, stay consistent, and keep solving! #DSA #LeetCode #CodingInterview #DataStructures #Algorithms #ProblemSolving #CodingPractice #SoftwareEngineer #Programming #Developers #TechInterview #CodeWithGandhi

Stack is one of the most important data structures used in many coding interview problems. 🧠 I came across these very helpful handwritten notes on stacks and thought they were worth sharing with the developer community. Topics covered include: 👇 📚 stack fundamentals 🔁 reverse a string using stack 🧩 delete middle element from stack ✅ valid parentheses problem ⬇️ insert element at bottom of stack 🔄 reverse stack using recursion 📊 next smaller element problem 📈 largest rectangle in histogram ⭐ celebrity problem ⚡ special stack with getMin in O(1) Around 40+ pages of handwritten notes explaining stack problems and concepts step by step. 📝 Great for students and developers revising DSA fundamentals or preparing for coding interviews. 🚀 Credits to the original creator for these amazing notes. 👏 Save this post so you can revisit the notes later. ⭐ #dsa #datastructures #algorithms #stack #codinginterview #programming #developers #coding #softwareengineering #leetcode #developercommunity #techlearning #learnprogramming #codingnotes #programmingnotes #devcommunity

🚀 Day 17/50 – LeetCode Challenge 🧩 Problem: Longest Common Subsequence (LCS) Today I worked on the Longest Common Subsequence problem, which is a classic example of Dynamic Programming and appears frequently in coding interviews. 📌 Problem Summary: Given two strings, the goal is to find the length of the longest subsequence that appears in both strings in the same order (not necessarily contiguous). Example: String 1 → "abcde" String 2 → "ace" Output → 3, because "ace" is the longest common subsequence. 🔍 Approach Used ✔ Used Dynamic Programming (DP) ✔ Created a 2D table to store intermediate results ✔ Compared characters of both strings step by step ✔ If characters matched → increase the subsequence length ✔ Otherwise → take the maximum value from previous results ⏱ Time Complexity: O(m × n) 📦 Space Complexity: O(m × n) 💡 Key Learning ✔ Understanding dynamic programming patterns ✔ Solving problems with overlapping subproblems ✔ Improving logical thinking for sequence comparison problems Problems like LCS are important because they form the foundation for many advanced algorithms used in bioinformatics, text comparison, and version control systems. Consistency in problem solving is the key to improvement 🚀 #LeetCode #DSA #DynamicProgramming #ProblemSolving #CodingJourney #FutureAIEngineer #Consistency

Solved Reverse Linked List II with optimal in-place pointer manipulation. Key takeaway: You don’t always need extra space—careful pointer rewiring can achieve O(1) space complexity while maintaining linear time. Approach highlights: Traverse to the left position while tracking the previous node Reverse the sublist using iterative pointer reversal Reconnect the reversed segment with the remaining list Performance: Runtime: 0 ms (100th percentile) Space: O(1) This problem is a solid reminder that mastering linked list fundamentals—especially pointer handling—can significantly improve both performance and confidence in low-level problem solving. Consistent practice is paying off. If you want, I can also make a slightly more storytelling-style or recruiter-focused version. #DataStructures #Algorithms #LinkedList #CodingInterview #LeetCode #ProblemSolving #SoftwareEngineering #Programming #JavaScript #CodeNewbie #100DaysOfCode #TechSkills #DeveloperJourney #CodingLife #DSA #TechCareer #LearnToCode #ComputerScience #CodingPractice #Placements

💻 Coding Interview Tips You Should Know💯 1️⃣ Understand the Problem First - Read the question carefully - Clarify constraints - Ask questions if needed 2️⃣ Think About the Brute Force Solution - Start with the simplest solution - Optimize later 3️⃣ Talk While Solving* - Explain your thinking - Show your logic 4️⃣ Use the Right Data Structure* - Choose the best structure for the problem - Common patterns: - Lookup problems: HashMap - Nested hierarchy: Tree - Order processing: Queue - Backtracking: Stack 5️⃣ Handle Edge Cases - Think about unusual inputs - Examples: empty input, large input, duplicates, negatives 6️⃣ Write Clean Code - Use meaningful variable names - Proper indentation - Simple logic 7️⃣ Analyze Complexity - Time Complexity: O(n) - Space Complexity: O(n) 8️⃣ Practice Patterns - Recognize problem patterns - Important patterns: Two Pointers, Sliding Window, Hashing, Binary Search, Dynamic Programming, Graph traversal 9️⃣ Test Your Code - Test manually - Check edge cases 🔟 Stay Calm When Stuck - Break the problem down - Explain your approach - Try small examples Follow KUNDAN KUMAR for more such content. #Java #development #devops #coding #coder #codinglife #code #programmingmemes #programmer

Building strong fundamentals step by step Today I worked on Array Pair-based coding challenges, solving problems that involved identifying and analyzing different types of pairs within arrays. 18 problems solved Score: 170 / 180 The challenges covered concepts such as: • Pair sum and difference conditions • Even and odd pair identification • Product-based pair problems • Prime-number based pair logic • Minimum/maximum pair calculations Practicing these problems strengthened my understanding of array traversal, nested loop logic, and problem-solving patterns often used in coding interviews. Consistent practice like this is helping me improve my problem-solving skills and algorithmic thinking every day. #Java #DataStructures #Arrays #ProblemSolving #CodingPractice #LearningInPublic

𝐂𝐨𝐝𝐢𝐧𝐠 is the missing puzzle piece that connects everything - whether you want to go into 𝐖𝐞𝐛 𝐃𝐞𝐯𝐞𝐥𝐨𝐩𝐦𝐞𝐧𝐭, 𝐃𝐚𝐭𝐚 𝐒𝐜𝐢𝐞𝐧𝐜𝐞, 𝐃𝐞𝐯𝐎𝐩𝐬, 𝐀𝐈, or 𝐒𝐨𝐟𝐭𝐰𝐚𝐫𝐞 𝐄𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠. When your fundamentals are strong, learning new technologies becomes 𝐞𝐚𝐬𝐢𝐞𝐫, understanding systems becomes 𝐜𝐥𝐞𝐚𝐫𝐞𝐫, and opportunities become easier to 𝐫𝐞𝐚𝐜𝐡. If your tech journey feels stuck or confusing, it may not be because you lack effort - you’re just 𝐦𝐢𝐬𝐬𝐢𝐧𝐠 𝐭𝐡𝐞 𝐫𝐢𝐠𝐡𝐭 𝐩𝐢𝐞𝐜𝐞. At Coding Blocks, we help you find that missing piece by focusing on 𝐬𝐭𝐫𝐨𝐧𝐠 𝐟𝐮𝐧𝐝𝐚𝐦𝐞𝐧𝐭𝐚𝐥𝐬, 𝐫𝐞𝐚𝐥 𝐩𝐫𝐨𝐛𝐥𝐞𝐦-𝐬𝐨𝐥𝐯𝐢𝐧𝐠, and 𝐭𝐡𝐞 𝐬𝐤𝐢𝐥𝐥𝐬 that actually matter in the industry. 𝐒𝐭𝐚𝐫𝐭 𝐰𝐢𝐭𝐡 𝐭𝐡𝐞 𝐛𝐚𝐬𝐢𝐜𝐬. 𝐁𝐮𝐢𝐥𝐝 𝐬𝐭𝐫𝐨𝐧𝐠 𝐜𝐨𝐝𝐢𝐧𝐠 𝐬𝐤𝐢𝐥𝐥𝐬. 𝐂𝐨𝐦𝐩𝐥𝐞𝐭𝐞 𝐭𝐡𝐞 𝐩𝐮𝐳𝐳𝐥𝐞 🧩 #Coding #TechSkills #CodingSkills #DSA #Java #Python #WebDevelopment #SoftwareEngineering #TechCareer #CodingJourney #Coders #ProgrammingLanguages #Programmer

In my previous posts, I covered the core OOP concepts — the foundation of system design. Today, we take the next step into SOLID principles, where code evolves from working → maintainable → scalable. SOLID is not just theory — it’s the foundation behind clean architecture, scalable systems, and maintainable enterprise code. If you’re preparing for interviews or aiming to move from coding → designing systems, mastering SOLID is a must. In today’s carousel, I’ve shared a simple introduction to SOLID and why it matters in real-world projects. Save this for revision, and follow along as we move deeper into system design thinking. 👉 Which SOLID principle do you find hardest to apply in real projects? #OOP #SOLID #SoftwareEngineering #SystemDesign #CleanCode #CodingInterview #DeveloperJourney #TechLearning #BackendDevelopment #DotNet #Java #Python #FullStackDeveloper

🚀 Day 3 / 45 – Consistency Over Motivation Continuing my 45-day focused preparation toward an IT role. Today’s progress: 💻 DSA (LeetCode Practice) Solved “Sort an Array” – Implemented sorting logic without relying on built-in shortcuts. Solved “Concatenation of Array” – Strengthened understanding of array indexing and traversal. Key takeaway: Understanding time complexity matters more than just getting correct output. O(N²) vs O(N log N) can decide whether your solution passes or fails at scale. 📊 Aptitude Practice Percentages Profit & Loss Ratios Focused on: Mental calculation speed Breaking down problems logically Avoiding common ratio-percentage mistakes 🎯 What This Journey Is Building Algorithmic thinking Mathematical clarity Implementation discipline Interview readiness No shortcuts. No random learning. Just structured improvement every single day. Next target: More array pattern problems Sliding window concepts Backend fundamentals continuation If you’re also preparing for tech roles, let’s stay consistent and grow together. #45DaysOfCode #DSA #LeetCode #Python #MERN #Aptitude #ProblemSolving #BackendDevelopment #JobPreparation