Cracking 3Sum on LeetCode with Optimized Approach

Solved “Add Two Numbers” on LeetCode with an efficient approach using linked list traversal and carry handling. Key highlights: Used a dummy node to simplify list construction Handled different list lengths seamlessly Managed carry propagation correctly across nodes Achieved optimal time complexity O(max(n, m)) Performance: Runtime: 3 ms (faster than ~55%) Memory: 61.25 MB (better than ~79%) This problem reinforces how mastering fundamentals like linked lists and pointer manipulation is crucial for writing clean and scalable solutions. Consistent practice is the real edge. #leetcode #datastructures #algorithms #coding #javascript #problemSolving #softwareengineering

Intersection of Arrays? Let the Set Do the Deduplication 🔍⚡ Solved LeetCode 349 today. Problem 🔍 Return the unique intersection of two arrays. Initial thought 🧠 Loop through both arrays and push matching elements. But this introduces duplicate results and unnecessary checks. Better approach 🚀 Use Sets for fast lookups and automatic uniqueness. 1️⃣ Convert first array to a Set 2️⃣ Iterate second array 3️⃣ If element exists in the set → add to result set Mental model 🧩 Set acts as both: • O(1) lookup structure • Duplicate filter Interview takeaway 🎯 If a problem requires unique results + existence checks, Sets simplify the solution dramatically. Practical insight 💡 Many array comparison problems become easier when one array is converted into a lookup structure. #DSA #LeetCode #Algorithms #JavaScript #HashSet #CodingInterview #InterviewPrep #DataStructures

Stop Shifting Elements. Use Two Pointers Instead ⚡📦 Solved LeetCode 283 (Move Zeroes) today. Problem 🔍 Move all 0s to the end while maintaining the order of non-zero elements. Initial thought 🧠 Shift elements or use extra array. Works, but increases time or space complexity. Better approach 🚀 Use two pointers: 1️⃣ One pointer tracks position for next non-zero 2️⃣ Traverse array 3️⃣ Swap non-zero elements forward Mental model 🧩 Partition the array: Left → non-zero zone Right → zero zone Interview takeaway 🎯 When rearranging elements in-place while preserving order, think two pointers + partitioning. Practical insight 💡 Avoid unnecessary swaps. Only move when needed to keep operations minimal. Time: O(n) Space: O(1) #DSA #LeetCode #Algorithms #TwoPointers #JavaScript #CodingInterview #InterviewPrep #ArrayProblems

🚀 LeetCode Problem Solved - Best Time to Buy and Sell Stock Today I solved the Best Time to Buy and Sell Stock problem on LeetCode using JavaScript with an optimized single-pass approach. 📊 Approach The goal is to determine the maximum profit from buying and selling a stock given its daily prices. The key idea is to: • Track the minimum price encountered so far • Calculate the potential profit for each day • Update the maximum profit whenever a higher profit is found This allows us to compute the result in one pass through the array. ⚡ Complexity 🔹 Time Complexity: O(n) – Traverse the prices array once 🔹 Space Complexity: O(1) – No extra data structures used ✅ Result ✔️ All test cases passed 📦 Constant space complexity Problems like this reinforce the importance of array traversal, state tracking, and optimizing brute-force solutions into efficient linear algorithms. Consistent practice with these problems strengthens DSA fundamentals and problem-solving skills for coding interviews. #leetcode #javascript #dsa #algorithms #codingpractice #softwareengineering #webdevelopment

Solved Linked List Cycle II using Floyd’s Cycle Detection Algorithm (Tortoise and Hare). The approach uses two pointers moving at different speeds to first detect the cycle and then identify the exact node where the cycle begins. Once the pointers meet, resetting one pointer to the head and moving both one step at a time leads them to the cycle start node. Key Takeaways: Efficient cycle detection in linked lists O(n) time complexity O(1) space complexity Classic two-pointer technique #DataStructures #Algorithms #LinkedList #JavaScript #LeetCode #ProblemSolving #CodingJourney #SoftwareEngineering

Solved the classic Reverse Linked List problem on LeetCode today. Approach used: Iterative pointer manipulation. Key idea: Maintain three pointers — prev, curr, and next. Algorithm flow: Store the next node (next = curr.next) Reverse the link (curr.next = prev) Move pointers forward (prev = curr, curr = next) Time Complexity: O(n) Space Complexity: O(1) It’s a simple problem conceptually, but mastering pointer manipulation is essential for understanding linked list internals and many advanced data structure problems. Consistently practicing these fundamentals strengthens problem-solving intuition and prepares you for more complex algorithmic challenges. #leetcode #datastructures #algorithms #javascript #linkedlist #problemSolving #codingPractice

🚀 𝗡𝗲𝘄 𝗣𝗥 𝗠𝗲𝗿𝗴𝗲𝗱 I recently tackled a fun logical puzzle: how to move all zeroes to the end of an array while maintaining the relative order of the non-zero elements. This challenge, which I've documented in my latest PR (https://lnkd.in/dSXWnSES), really tested my ⚙️ 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵 to array manipulation. My solution involved iterating through the array and using a pointer to keep track of the position where the next non-zero element should be placed. This allowed me to effectively "compress" the non-zero elements to the front, implicitly leaving zeroes at the end. During the process, I leaned on dry runs to trace the array's state and visualize the pointer movements. When I hit a snag, the debugger was invaluable for stepping through the logic line by line and understanding exactly where my assumptions were off. A key takeaway for me was the power of in-place modification and how a well-placed pointer can simplify array problems significantly. How do you ⚙️ 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵 similar array manipulation challenges? Share your strategies below! 📦 Repo: https://lnkd.in/dSXWnSES #ArrayManipulation #JavaScript #Algorithms #ProblemSolving #CodingChallenge #DataStructures #InPlaceAlgorithms #LogicalReasoning #SoftwareDevelopment #LeetCodeStyle

When Prefix Sums Repeat, Something Interesting Happens 🔁📊 Solved LeetCode 523 today. Problem 🔍 Check if a subarray of length ≥ 2 exists whose sum is divisible by k. Initial thought 🧠 Check every subarray using prefix sums. But that quickly becomes O(n²). Better approach 🚀 Use Prefix Sum + Remainder HashMap. Store the first index where each remainder appears. If the same remainder appears again and currentIndex - previousIndex >= 2, a valid subarray exists. Mental model 🧩 If: prefix[j] % k = prefix[i] % k Then: prefix[j] - prefix[i] is divisible by k. Interview takeaway 🎯 Subarray + divisibility → Prefix Sum + Remainder tracking. Practical insight 💡 Store the first occurrence of each remainder to maximize subarray length detection. This same pattern appears in problems like 974 and 560. #DSA #LeetCode #Algorithms #PrefixSum #HashMap #JavaScript #CodingInterview #InterviewPrep

🚀 LeetCode Problem Solved – Reverse String Solved the Reverse String problem on LeetCode using JavaScript with an optimized in-place approach. ✅ Key Idea: Reverse the string by swapping characters from the start and end of the same array, modifying it directly without creating any extra array. 🔹 Time Complexity: O(n) 🔹 Space Complexity: O(1) – No extra space used (in-place modification) 💡 Approach: • Use a two-pointer technique • One pointer starts from the beginning of the array • Another pointer starts from the end • Swap characters and move both pointers toward the center until they meet 📊 Result ✔️ All test cases passed ⚡ Runtime: 0 ms 📦 Space Complexity: O(1) Consistently practicing problems like this helps strengthen Data Structures & Algorithms fundamentals and improves problem-solving skills for coding interviews. #leetcode #javascript #dsa #twopointers #programming #codingpractice #softwareengineering

🚀 𝗡𝗲𝘄 𝗣𝗥 𝗠𝗲𝗿𝗴𝗲𝗱 I recently tackled a common but insightful logical challenge: finding the second largest number in an array. This 🧩 𝗣𝗿𝗼𝗯𝗹𝗲𝗺 often appears in technical interviews and requires careful thought to handle edge cases effectively. My ⚙️ 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵 involved iterating through the array using JavaScript, keeping track of both the largest and second largest numbers encountered so far. I initialized variables for both to handle the initial comparisons and ensured proper updates as I scanned the array. The 🐞 𝗗𝗲𝗯𝘂𝗴𝗴𝗶𝗻𝗴 𝗣𝗿𝗼𝗰𝗲𝘀𝘀 was crucial. I performed several dry runs mentally to trace the logic, visualized the flow of variables, and used console logs to verify the state of 'largest' and 'secondLargest' at each step. This helped me catch and correct a minor flaw in the initial comparison logic. A 📚 𝗞𝗲𝘆 𝗟𝗲𝗮𝗿𝗻𝗶𝗻𝗴 for me was the importance of precise variable initialization and comparison order to correctly handle duplicate maximum values and empty or single-element arrays. Check out the solution in my latest pull request here: https://lnkd.in/dCcT48U9 How do you ⚙️ 𝗔𝗽𝗽𝗿𝗼𝗮𝗰𝗵 finding the nth largest element in an array? Share your favorite techniques below! 📦 Repo: https://lnkd.in/dCcT48U9 #ArrayManipulation #JavaScript #Algorithm #ProblemSolving #CodingChallenge #Debugging #SoftwareEngineering #LogicalThinking #DataStructures #LearnToCode