Linked List Two-Pointer Techniques in Java

🚀 Daily DSA Practice – Day 20 | Advanced Linked List Manipulation (Java) As part of my ongoing Data Structures & Algorithms preparation, today I focused on advanced linked list problems involving complex pointer relationships, duplicate handling, and node swapping, all implemented using Java. 📌 Problems Solved (LeetCode): • 138. Copy List with Random Pointer – Created a deep copy using efficient node mapping to preserve random pointers • 82. Remove Duplicates from Sorted List II – Removed all nodes with duplicate values using careful pointer traversal • 24. Swap Nodes in Pairs – Swapped adjacent nodes using in-place pointer manipulation 🎯 Key Learnings: ✔ Improved handling of complex node relationships and deep copy logic ✔ Strengthened understanding of duplicate elimination in sorted lists ✔ Mastered safe node swapping without modifying node values ✔ Implemented O(n) time and O(1) / O(n) space optimized Java solutions These problems pushed my understanding of linked list internals and enhanced my confidence in solving medium-level interview problems involving non-trivial pointer logic. #DSA #LeetCode #Java #LinkedList #ProblemSolving #BackendDeveloper #SoftwareEngineer #InterviewPreparation

🚀 Daily DSA Practice – Day 31 | Monotonic Queue & Advanced Sliding Window (Java) As part of my ongoing Data Structures & Algorithms preparation, today I focused on mastering monotonic queue techniques and advanced sliding window patterns, which are widely used in optimization and range-query problems. 📌 Problems Solved (LeetCode): • 239. Sliding Window Maximum – Implemented a monotonic decreasing deque to efficiently track maximum values in each window • 1438. Longest Continuous Subarray With Absolute Diff ≤ Limit – Used two monotonic deques to maintain window minimum and maximum dynamically • 862. Shortest Subarray with Sum at Least K – Applied prefix sums with a monotonic deque to find the shortest valid subarray efficiently 🎯 Key Learnings: ✔ Learned how monotonic queues maintain min/max in O(1) amortized time ✔ Combined sliding window with deque optimization ✔ Solved range-based optimization problems efficiently ✔ Strengthened advanced queue patterns used in hard interview questions These problems demonstrated how monotonic queues are powerful for window-based optimizations and high-performance array processing, commonly tested in top-tier technical interviews. #DSA #LeetCode #Java #Queue #Deque #SlidingWindow #MonotonicQueue #ProblemSolving #InterviewPreparation #BackendDeveloper #SoftwareEngineer

DSA Practice | Pair Sum Problem (Brute Force Approach) :- Problem Statement: Given an array of integers and a target value, check whether any pair of elements in the array sums up to the target. Practiced a Data Structures and Algorithms problem using Java, where the task was to determine whether a pair of elements in an array adds up to a given target value. I implemented a brute-force approach using nested loops to check all possible unique pairs in the array. To keep the solution clean and efficient, I used a boolean flag instead of strings and applied proper loop control to stop unnecessary comparisons once the required condition was met. This problem helped reinforce important Java and DSA concepts such as: Pair-wise comparison using nested loops Using boolean flags for condition tracking Writing clean, readable, and interview-friendly code Understanding time and space complexity Time Complexity: O(n²) #DSA #JAVA

🚀 Solved: Remove Nth Node From End of a Linked List (Java) Today I revisited a classic Linked List problem and solved it using the Two Pointer Technique 🧠✨ 💡 Problem Statement Remove the N-th node from the end of a singly linked list efficiently. ✅ Approach Used 🔹 Fast Pointer moves n steps ahead 🔹 Slow Pointer starts from the head 🔹 Both pointers move together until the fast pointer reaches the end 🔹 The slow pointer then points to the node just before the one to be removed 🔹 Adjusting the link removes the target node safely ⚡ Why this approach works well ✔ Solves the problem in one pass ✔ No extra data structures required ✔ Time Complexity: O(n) ✔ Space Complexity: O(1) 📌 Key Learning 👉 Two-pointer techniques are extremely effective for optimizing linked list problems and avoiding unnecessary traversals. 📈 Consistently practicing such problems improves logical thinking and confidence in DSA. 💬 Happy to discuss or learn alternative approaches! 🔗 #Java #LinkedList #TwoPointers #DSA #ProblemSolving #CodingJourney #LeetCode #SoftwareEngineer 🚀

🚀 Day 32 Out of #365DaysOfCode -LeetCode ✅ LeetCode Problem Solved: Delete the Middle Node of a Linked List I solved the Delete the Middle Node problem on LeetCode by analyzing the length of the linked list and removing the middle element in a clean and structured way. 🔹 Approach Used: First traversed the linked list to calculate its total size Identified the middle index using size / 2 Traversed again to reach the node just before the middle Adjusted pointers to delete the middle node safely 🔹 Key Concepts Practiced: Linked List traversal Pointer manipulation Edge case handling (empty list or single node) 🔹 Complexity Analysis: Time Complexity: O(n) Space Complexity: O(1) 📌 This problem helped strengthen my understanding of linked list operations and pointer-based problem solving in Java. #LeetCode #Java #LinkedList #DSA #ProblemSolving #CodingPractice #InterviewPreparation #LearningJourney Github link: https://lnkd.in/gGUy_MKZ

 Day 10/100 Q 12 – Remove Duplicates from Sorted Array (DSA) Today’s problem was all about in-place array manipulation and two-pointer technique. 📌 Problem Statement Given a sorted integer array, remove duplicates in-place so that each unique element appears only once and return the count of unique elements. 🧠 Key Insight Since the array is already sorted, duplicates appear next to each other. Using two pointers, we can overwrite duplicates and keep all unique elements at the beginning of the array without using extra space. ⚙️ Approach Use one pointer to track the last unique element Traverse the array with another pointer Update the array when a new unique element is found ⏱ Complexity Time: O(n) Space: O(1) 💡 What I Learned How sorting simplifies duplicate problems Practical use of the two-pointer technique Writing space-optimized solutions 🔁 On to the next challenge! Consistency > Motivation 💪 #100DaysOfDSA #DSA #Arrays #TwoPointers #Java #ProblemSolving #LeetCode #CodingJourney #DailyLearning

🚀 Daily DSA Practice – Day 21 | Advanced Linked List & System Design Patterns (Java) As part of my continued Data Structures & Algorithms preparation, today I tackled advanced linked list problems that combine data structure design, multi-level traversal, and efficient merging strategies using Java. 📌 Problems Solved (LeetCode): • 146. LRU Cache – Designed an efficient cache using HashMap + Doubly Linked List to achieve O(1) get and put operations • 430. Flatten a Multilevel Doubly Linked List – Flattened a multi-level structure using depth-first traversal while maintaining list integrity • 23. Merge k Sorted Lists – Merged multiple sorted linked lists using a Min Heap (PriorityQueue) for optimal performance 🎯 Key Learnings: ✔ Combined multiple data structures to design efficient systems ✔ Strengthened understanding of doubly linked list operations ✔ Applied heap-based optimization for large-scale list merging ✔ Built scalable, interview-ready Java solutions with optimal time complexity Solving these problems enhanced my confidence in handling complex linked list scenarios and system-level interview questions frequently asked in top tech companies. #DSA #LeetCode #Java #LinkedList #LRUCache #Heap #ProblemSolving #BackendDeveloper #SoftwareEngineer #InterviewPreparation

🚀 Daily DSA Practice – Day 30 | Circular Queue, Deque & Sliding Window (Java) As part of my ongoing Data Structures & Algorithms preparation, today I focused on advanced queue structures including circular queues, deques, and sliding window techniques, implementing efficient solutions in Java. 📌 Problems Solved (LeetCode): • 622. Design Circular Queue – Implemented an array-based circular queue to handle efficient enqueue and dequeue operations without wasted space • 641. Design Circular Deque – Built a double-ended queue supporting insertions and deletions from both ends with constant time complexity • 346. Moving Average from Data Stream – Used a queue with a sliding window to calculate running averages efficiently 🎯 Key Learnings: ✔ Understood circular queue indexing and wrap-around logic ✔ Practiced implementing deque operations from scratch ✔ Applied sliding window techniques using queues ✔ Strengthened time- and space-efficient queue design patterns These problems highlighted how advanced queue variants and sliding window methods are widely used in streaming data processing and system design interviews. #DSA #LeetCode #Java #Queue #Deque #SlidingWindow #ProblemSolving #InterviewPreparation #BackendDeveloper #SoftwareEngineer

Today I practiced a few important string-based problems on LeetCode: ✅ 171 – Excel Sheet Column Number → Learned base-26 conversion logic using characters. ✅ 205 – Isomorphic Strings → Used two-way mapping to ensure one-to-one character relationships. ✅ 242 – Valid Anagram → Applied frequency array technique for efficient comparison. 💡 These problems strengthened my understanding of: Character mapping Frequency counting String traversal logic Writing clean, optimized Java code 📈 Staying consistent and improving problem-solving skills step by step. #LeetCode #DSA #Java #ProblemSolving #CodingPractice #Consistency #InterviewPreparation

🚀 Day 27 | Cracking LeetCode #29 – Divide Two Integers (Java) ⚙️☕ 📌 Problem: Divide Two Integers ⚠️ Constraint: No multiplication, division, or mod operator allowed 🎯 Difficulty: Medium 💻 Language: Java 🧠 Core Logic & Approach To solve this efficiently, I used bit manipulation and doubling technique: ➤ Handled edge cases upfront • Divisor = 1 • Overflow case: Integer.MIN_VALUE / -1 ➤ Converted both numbers to negative values to avoid overflow ➤ Used left shift (<<) to repeatedly double the divisor ➤ Subtracted the largest possible chunk from dividend ➤ Counted how many times subtraction was performed ➤ Applied sign logic at the end to return the correct result ⚡ Performance Highlights ⏱️ Runtime: 1 ms ⚡ (Beats 90.91%) 💾 Memory: 42.76 MB (Beats 33.63%) 🔍 Key Takeaways ✔️ Bit manipulation can replace arithmetic operators ✔️ Handling integer overflow is crucial in low-level problems ✔️ Converting to negative simplifies boundary conditions ✔️ Optimized logic drastically improves performance 📈 DSA Progress = Daily Consistency + Deep Thinking Learning how problems work under the hood, not just solving them 🚀🔥 #Day27 #LeetCode #Java #DSA #BitManipulation #ProblemSolving #CodingJourney #LearningInPublic #SoftwareEngineering