LeetCode Challenge: Contains Duplicate II Solution

Day 101 - LeetCode Journey Solved LeetCode 856: Score of Parentheses ✅ Looks tricky at first, but turns out to be a neat pattern problem. Instead of using a stack, used depth tracking + bit manipulation to calculate score efficiently. Core idea: Every "()" contributes 2^depth So just track depth and add score at the right moment. Key learnings: • Understanding pattern inside parentheses • Using depth instead of extra space • Bit manipulation for optimization ⚡ • Clean O(n) solution without stack ✅ All test cases passed ⚡ O(n) time | O(1) space Simple logic, powerful result 💡 #LeetCode #DSA #Stack #BitManipulation #Java #CodingJourney #ProblemSolving #InterviewPrep

Day 56 : Crushing Binary Trees on LeetCode 💡 Today’s live practical session in Alpha Plus 7.0 We focused on some of the most challenging Binary Tree questions on LeetCode, breaking down the logic behind them. What I practiced today: ✅ Tree Diameter: understand the logic to calculate the absolute longest path between any two nodes in the entire tree. ✅ Maximum Path Sum: Tackled a famous "Hard" level problem! Figured out how to find the path with the highest possible sum, even if it doesn't pass through the root. ✅ Target Deletion: Wrote the recursive code to systematically find and delete leaf nodes that match a specific target value. #BinaryTree #LeetCode #ProblemSolving #DSA #Java #SoftwareEngineering #100DaysOfCode #ApnaCollege

🚀 Day 69 — LeetCode Practice 🚀 Today’s focus was on string manipulation and careful indexing. ✅ Problem solved today: 🔹 Find Common Characters 💡 Key learnings from today: • Understood how to find common characters across multiple strings • Learned the importance of character frequency counting • Practiced handling nested loops efficiently • Realized how small mistakes in indexing can affect the entire logic • Improved attention to detail while working with strings Initially, I made a mistake by using the wrong variable inside charAt(). This caused incorrect indexing, which can either lead to wrong output or even StringIndexOutOfBoundsException. After fixing it, the logic worked perfectly by correctly comparing characters and tracking their minimum frequency across all words. This problem reinforced an important lesson: Sometimes errors are not in logic — but in small details like indexing and variable usage. Accuracy matters as much as logic. Step by step, getting better 💪 On to Day 70 🚀 #Day69 #DSA #LeetCode #ProblemSolving #Java #CodingJourney #Consistency #FutureEngineer

Day 20/100 🚀 | LeetCode Grind Cracked “Guess Number Higher or Lower” using Binary Search 🎯 Optimized the approach by narrowing down the search space efficiently with each guess — classic divide & conquer in action. 💡 Key Takeaway: When the search space is sorted and bounded, Binary Search is your best friend. ⚡ Runtime: 0 ms (Beats 100%) 📊 Efficient and clean implementation Consistency > Intensity. Showing up every day 💪 #Day20 #100DaysOfCode #LeetCode #DSA #BinarySearch #CodingJourney #Java #ProblemSolving

100 Days of Code Day - 24 🔁 Swap Nodes in Pairs – LeetCode Problem Solved a classic Linked List problem today! 💡 👉 Given a linked list, swap every two adjacent nodes without modifying values — only changing the links. ✅ Example: Input: [1,2,3,4] Output: [2,1,4,3] 💭 Approach: Used a dummy node and pointer manipulation to efficiently swap nodes in O(n) time and O(1) space. 📌 Key Learning: Understanding pointer handling is crucial for mastering Linked Lists. #LeetCode #Java #DSA #LinkedList #CodingJourney #ProblemSolving

🚀 Day 17 of My LeetCode Journey 📌 Solved: LeetCode #11 – Container With Most Water Today’s problem was a great example of applying the Two Pointer Approach efficiently. 🔍 Problem Summary: Given an array of heights, find two lines that together with the x-axis form a container that holds the maximum amount of water. 💡 Approach Used: Started with two pointers at both ends Calculated area using: min(height[left], height[right]) × width Moved the pointer with smaller height to maximize area ⚡ Key Learning: Instead of checking all pairs (O(n²)), we can optimize to O(n) using the two-pointer technique. 🧠 Time Complexity: O(n) 📦 Space Complexity: O(1) 🔥 Consistency is the key — learning something new every day! #LeetCode #DSA #Java #CodingJourney #ProblemSolving #100DaysOfCode

🚀 LeetCode Challenge 3/50 💡 Approach: Two Pointer (In-Place) The straightforward way uses an extra array — but the problem specifically says no copying! So I used the Two Pointer technique to solve it in-place with a single pass. 🔍 Key Insight: → Use a 'left' pointer to track where the next non-zero element belongs → Traverse with 'right' pointer — place non-zeros at left, then increment → Fill remaining positions with 0s at the end 📈 Complexity: ✅ Time: O(n) — single pass ✅ Space: O(1) — no extra array, truly in-place Sometimes the constraint IS the optimization. Working within limits pushes us to think smarter! 🧠 #LeetCode #DSA #TwoPointer #Java #ADA #PBL2 #LeetCodeChallenge #Day3of50 #CodingJourney #ComputerEngineering #AlgorithmDesign #MoveZeroes

💡 Day 54 of LeetCode Problem Solved! 🔧 🌟 560. Subarray Sum Equals K 🌟 🔗 Solution Code: https://lnkd.in/g5VwiFKd 🧠 Approach: Prefix Sum & Hash Map Store cumulative sums in a Map Check for (current_sum - k) to find matching subarrays in one pass ⚡ Key Learning: Mastering the Prefix Sum + HashMap pattern is a game-changer for transforming $O(n^2)$ subarray problems into efficient $O(n)$ solutions. ⏱️ Complexity: Time: O(n) Space: O(n) #LeetCode #Java #DSA #ProblemSolving #Consistency #100DaysOfCode #CodingJourney #PrefixSum #DataStructures

🚀 LeetCode Challenge 4/50 💡 Approach: Reverse Traversal (No Split!) The easy way out? s.trim().split(" ") — but that creates an extra array and costs O(n) space. Instead, I traversed from the end of the string directly! 🔍 Key Insight: → Start from the last character → Skip any trailing spaces first → Count characters until the next space — that's your answer! 📈 Complexity: ✅ Time: O(n) — at most one full scan ✅ Space: O(1) — zero extra memory used The best solution isn't always the most obvious one. Sometimes looking from a different angle (literally, from the end!) makes all the difference. 🔄 #LeetCode #DSA #StringManipulation #Java #ADA #PBL2 #LeetCodeChallenge #Day4of50 #CodingJourney #ComputerEngineering #AlgorithmDesign #LengthOfLastWord

🚀 Day 71/100 – LeetCode Challenge Solved: Remove Duplicates from Sorted List II (Medium) Today’s problem was a great test of Linked List manipulation and handling edge cases efficiently. 🔍 Key Insight: Since the list is sorted, duplicates appear consecutively. Instead of keeping one copy, the challenge is to remove all nodes with duplicate values, leaving only distinct elements. 💡 Approach: Used a dummy node to handle edge cases Applied two-pointer technique (prev & current) Skipped entire duplicate sequences in one pass ⚡ Result: Runtime: 0 ms (Beats 100%) Space Complexity: O(1) 🎯 Key Learning: Handling duplicates in linked lists requires careful pointer updates — especially when the head itself is part of duplicates. Consistency is key 🔥 #Day71 #LeetCode #100DaysOfCode #Java #DataStructures #LinkedList #ProblemSolving #CodingJourney