Mastering Java with LeetCode: Hashing and Data Structures

🚀 Mastering Java Through LeetCode 🧠 Day 20 of My DSA Journey Today I solved another problem from the LeetCode 75 list to improve my understanding of HashMap and HashSet concepts and strengthen my problem-solving skills. 📌 LeetCode Problem Solved Today: Q.1207 – Unique Number of Occurrences 💡 Problem Statement: Given an integer array arr, return true if the number of occurrences of each value in the array is unique, otherwise return false. 🧩 Example 1: Input: [1,2,2,1,1,3] Output: true 🧩 Example 2: Input: [1,2] Output: false Key Learning: Today I learned how to efficiently solve problems using Hashing techniques: ✔️ Use HashMap to count frequency of each number ✔️ Use HashSet to check if frequencies are unique ✔️ If any frequency repeats → return false 🧠 Approach: 1️⃣ Traverse array and store frequency using getOrDefault() 2️⃣ Traverse map values 3️⃣ Check duplicates using HashSet ⏱️ Complexity: Time Complexity: O(n) Space Complexity: O(n) This problem helped me understand how frequency counting + uniqueness checking works in real interview scenarios. Consistency is the key — solving problems daily to become a better software engineer 💻 #LeetCode #Java #DSA #ProblemSolving #CodingJourney #LearningInPublic #SoftwareDevelopment #Programming #Coding #Tech #Developers #100DaysOfCode #TechCareer #InterviewPreparation #HashMap #HashSet #CodingPractice #PGCP #CDAC #LeetCode75

🚀 Mastering Java Through LeetCode 🧠 Day 23 of My DSA Journey Today I solved an interesting stack-based problem that improved my understanding of string manipulation and data structures. 📌 LeetCode Problem Solved Today: Q. 2390 – Removing Stars From a String 💡 Problem Statement: Given a string containing *, remove each star along with the closest non-star character to its left. Approach: I used a Stack-based approach: Traverse the string character by character If the character is not *, push it into the stack If the character is *, pop the top element from the stack Finally, build the result string from the stack ✨ This approach works efficiently in O(n) time and ensures all operations are handled correctly. 📈 Key Learnings: Stack helps in handling last-in-first-out (LIFO) operations Efficient string manipulation using StringBuilder Importance of choosing the right data structure 🔥 Consistency is key — improving problem-solving skills every day! #Java #DSA #LeetCode #CodingJourney #SoftwareDevelopment #ProblemSolving #Tech #Learning #Developers #OpenToWork #CAC

Day 38 – 44 of my Frontlines EduTech (FLM) AI-Powered Java Full Stack Journey Day 38: Started learning Collections in Java. Focused on ArrayList and how it stores dynamic data. Understood how it is different from arrays. Day 39: Learned about Iterator. Used it to traverse elements in collections. It made looping through data more clean and flexible. Day 40: Explored Set interface. Learned that it stores only unique elements. Good for removing duplicates from data. Day 41: Learned Map in Java. Stores data in key-value pairs. Very useful for real-world applications. Day 42: Covered Enum and Command Line Arguments. Also learned Static and Instance Blocks. Understood when and how they are executed. Day 43: Learned Clone, Comparator, and Comparable. Used for copying objects and sorting data. Important for customizing sorting logic. Day 44: Solved problem on frequency of characters. Used logic with collections to count occurrences. Good practice for improving problem-solving skills. Consistent learning, step by step. Fayaz S 🔗 Github: https://lnkd.in/gV_uis3J #Java #Collections #CodingJourney #100DaysOfCode #LearnJava #FullStack 🚀

🚀 Mastering Java Through LeetCode 🧠 Day 33 Not all nodes are “Good”… but finding them made me better at Trees 📌 LeetCode Problem Solved: Q.1448 – Count Good Nodes in Binary Tree 💭 Problem Summary: A node is called “Good” if no node on the path from root to it has a greater value. 🎯 Approach: ✔ Used DFS (Depth First Search) ✔ Tracked the maximum value seen so far in the path ✔ If current node ≥ maxSoFar → count it as a Good Node ✔ Updated max and continued recursion 🧠 Key Insight: Instead of storing the full path, just carry maxSoFar — simple yet powerful optimization! 💡 Complexity: ⏱ Time: O(N) 📦 Space: O(H) 🔥 What I Learned: How to maintain state during recursion Clean way to solve tree problems using DFS Thinking in terms of path-based conditions Consistency builds confidence 💪 Day 33 done… Let’s keep going 🚀 #Java #LeetCode #DataStructures #Algorithms #CodingJourney #100DaysOfCode #DSA #Tech #Learning

Mastering Java through LeetCode Day 37 of #LeetCode Challenge Today I solved Lowest Common Ancestor of a Binary Tree Problem Insight: The goal is to find the lowest node in a binary tree that has both given nodes as descendants (a node can be a descendant of itself). Approach I used: Used DFS + Recursion If the current node is null or matches one of the targets → return it Recursively search left and right subtrees If both sides return non-null → current node is the LCA ⚡ Key Learning: Understanding how recursion propagates results upward is crucial for solving tree problems efficiently. ⏱️ Complexity: Time: O(n) Space: O(h) Consistency > Intensity Improving problem-solving skills one day at a time! #DataStructures #Algorithms #Java #CodingJourney #SoftwareEngineering #OpenToWork #LeetCode #LearningInPublic

On Day 28 of my Java learning journey, I explored the Collections Framework, which provides powerful data structures to store and manage data efficiently. This concept is widely used in real-world applications. 📚 What I Learned Today Today I learned: ✔ What collections are and why they are important ✔ Using ArrayList for dynamic data storage ✔ Using HashSet to remove duplicates ✔ Using HashMap for key-value data storage 💻 Practice Work To apply my learning, I implemented: • Programs using ArrayList to store elements • HashSet to handle unique values • HashMap to manage key-value pairs 🎯 Key Takeaway Collections make data handling easier and more efficient compared to traditional arrays. They are essential for building scalable and efficient applications. Learning these advanced concepts is boosting my confidence in Java programming. #Java #Programming #LearningInPublic #CodingJourney #SoftwareDevelopment #Collections

🚀 DSA Journey — LeetCode Practice 📌 Problem: N-ary Tree Preorder Traversal (LeetCode 589) 💻 Language: Java 🔹 Approach: To solve this problem, I used Depth-First Search (DFS) with Recursion to traverse the N-ary tree in preorder format. • Visit the root node first • Store the root value in the result list • Recursively traverse all children from left to right • Follow Preorder pattern: Root → Children This approach works efficiently because recursion naturally follows the preorder traversal structure. ⏱ Time Complexity: O(n) 🧩 Space Complexity: O(n) (including recursion stack) 📖 Key Learning: This problem strengthened my understanding of DFS, recursion, and N-ary tree traversal. It also reinforced the preorder pattern (Root → Children), which is a fundamental concept used in many tree-based problems 💡 #DSA #Java #LeetCode #ProblemSolving #CodingJourney #LearningInPublic #NaryTree #DFS #Recursion #TreeTraversal

🚀 Today’s Learning: ArrayDeque in Java In today’s session, I explored the concept of ArrayDeque, a powerful and efficient data structure in Java. 🔹 Learned the properties of ArrayDeque such as dynamic resizing and fast insertion/deletion 🔹 Explored important methods like addFirst(), addLast(), offer(), poll(), peek(), remove() 🔹 Understood how to access elements using loops and iterators 🔹 Discovered when to use ArrayDeque for both stack (LIFO) and queue (FIFO) operations 💡 Key Insight: ArrayDeque is a better alternative to Stack and often more efficient than LinkedList for queue operations. Excited to implement these concepts in coding and real-world applications! 💻✨ TAP Academy Bibek Singh #Java #ArrayDeque #DataStructures #Coding #LearningJourney #InterviewPrep

🌱 Day 87/90 – Pattern Recognition & Distance Optimization | #DSAPattern Today’s practice was focused on identifying patterns in arrays and optimizing distance calculations between elements. Problems like this help build intuition for tracking indices efficiently and avoiding unnecessary comparisons. The key idea is to store positions smartly and minimize the distance using optimal traversal techniques instead of brute force. The goal? Train my brain to quickly recognize repeating patterns and compute results with minimal time complexity. 🧠 Problem I Practiced Today 👇 ✔ 3740. Minimum Distance Between Three Equal Elements This problem involves finding the minimum distance between any three equal elements in an array. Key insight: Track indices of each element using a HashMap and compute the distance between consecutive occurrences efficiently. The tricky part is ensuring that only valid triplets are considered while minimizing the distance in a single pass. 💡 What I Focused On Today 👉 Index tracking using HashMap 👉 Pattern recognition in arrays 👉 Optimizing distance calculations 👉 Avoiding unnecessary nested loops 👉 Clean and efficient Java implementation One important reminder from today’s practice: Brute force may give results—but pattern recognition and optimization make solutions scalable and interview-ready. ✅ Day 87 done – staying consistent and getting sharper every day 🚀💪 #Day87Done #90DaysOfDSA #DSAPattern #LeetCode #Algorithms #Java #DataStructures #CodingInterviewPrep #JavaDSA #Programming #CompetitiveProgramming #CodingJourney #ThinkInPatterns #PlacementPreparation

Today’s learning sprint 🚀 Dived into some core Java fundamentals that every developer should have crystal clear: 🔹 Data Types Understanding how real-world data is converted into binary and stored. Focused on integer types — byte, short, int, long — and how memory representation works. 🔹 Main Method The entry point of every Java program: public static void main(String[] args) Broke down each keyword and understood why it exists, not just memorizing it. 🔹 Object-Oriented Thinking Shifted perspective to seeing everything as objects: * Objects = State (data) + Behavior (methods) * Learned how Java uses new to create objects * Simple example: Car c1 = new Car(); 💡 Key takeaway: It’s not about memorizing syntax — it’s about understanding how things actually work under the hood. Grateful for the guidance and structured learning 🙌 Special thanks to TAP Academy and Bibek Singh for making these concepts clear and practical. Also grateful to Global Academy Of Technology Slowly building strong foundations, one concept at a time. #Java #Programming #CodingJourney #OOP #ComputerScience #LearningInPublic