Implementing Zigzag Level Order Traversal with BFS

✅ Learned to solve “Remove Duplicates from Sorted Array” (in-place, O(n) time, O(1) space)! Sorted input means every duplicate sits next to its twin—perfect setup for the two-pointer pattern: scan once, write uniques forward, and return the count k while keeping the first k positions clean and ordered. What clicked: - Two pointers: one scans, one writes uniques forward - Skip repeats deterministically thanks to sorting - Edge cases covered: empty array, all duplicates, negatives, mixed ranges Level-ups next: “Remove Duplicates II” (allow at most twice) and “Remove Element” to deepen the pattern muscle. What’s your favorite twist on this technique? 🚀 #LeetCode #TwoPointers #Arrays #InPlace #DSA #Algorithms #InterviewPrep #ProblemSolving #TimeComplexity #CodingChallenge #Python #SoftwareEngineering

Day 5 of #100DaysOfLeetCode Problem: 54. Spiral Matrix Category: Arrays / Matrix Traversal Today’s challenge focused on traversing a 2D matrix in spiral order and returning all elements in that pattern. This problem was really fun to solve because it required handling multiple edge cases while maintaining clean traversal logic. 🧠 Key Learnings: Used the concept of repeatedly peeling off the outer layer of the matrix. Traversed top row → right column → bottom row → left column in sequence. Understood the importance of checking matrix boundaries after each step to avoid index errors. Improved logical thinking for problems involving nested data structures. 🎯 Takeaway: Matrix traversal problems are all about maintaining control over direction and boundaries — once that’s handled, the logic flows smoothly. #LeetCode #100DaysOfCode #ProblemSolving #CodingJourney #Matrix #Arrays #Python #AIEngineer #Consistency

Day 13 of #100DaysOfLeetCode Problem: 88. Merge Sorted Array Category: Arrays / Sorting / Two Pointers Today’s challenge focused on merging two sorted arrays into one, maintaining the sorted order. It’s a simple yet powerful problem that tests your understanding of array indices, merging logic, and in-place updates. 🧠 Key Learnings: Extended the first array by adding elements from the second, then sorted the combined list. Reinforced the importance of efficient merging techniques for sorted sequences. Understood how in-place operations can reduce memory usage in practical scenarios. Strengthened logic building around sorting fundamentals and index-based insertion. 🎯 Takeaway: Even simple array problems help build strong fundamentals in sorting and data manipulation — the key to mastering larger algorithmic challenges. #LeetCode #100DaysOfCode #ProblemSolving #CodingJourney #Arrays #Sorting #Python #AIEngineer #Consistency

Day 30 / 100 – Majority Element II (LeetCode #229) Today’s challenge was all about identifying numbers that appear more than ⌊ n/3 ⌋ times in an array. This problem was a great way to explore the Boyer–Moore Voting Algorithm, an elegant and efficient method to find potential majority elements without using extra space. 🔍 Key Learnings Understanding how counters and candidates evolve in an iterative approach Strengthening logic for pattern recognition and frequency analysis Realizing how efficient algorithms can reduce time and memory usage 💭 Thought of the Day Consistency isn’t just about showing up — it’s about learning smarter each day. Every new problem isn’t a repetition; it’s a refinement of logic and discipline. 🔗 Problem Link:https://lnkd.in/gfiGVueC #100DaysOfCode #Day30 #LeetCode #Python #ProblemSolving #CodingChallenge #DataStructures #Algorithms #LearningJourney #CodeEveryday #TechGrowth

🚀 Day 3 of #100DaysofDSA Today’s focus was on the “Set Matrix Zeroes” problem — a classic array-matrix question that tests both logic and optimization thinking It began with the brute-force idea: storing all zero positions and then marking corresponding rows and columns later. It works but takes O(m × n) time and O(m + n) extra space. Next, then explored a better approach using two auxiliary arrays to track which rows and columns should be zeroed. This improved the clarity but still consumed additional memory and space. Finally, then to reduce the complexity I tackled the optimal solution, which achieves O(1) extra space by using the first row and first column of the matrix itself as markers. A small Boolean flag handles the edge case when the first row contains a zero. This subtle observation transforms the logic completely — turning a memory-heavy method into a clean in-place algorithm. It was a good reminder that optimization isn’t just about speed — it’s about finding elegance in constraints. #100DaysOfDSA #MatrixProblems #Optimization #SpaceComplexity #Python #ProblemSolving

DAY-1:CODING CHALLENGE 1.Longest common Prefix substring from given string as input 2.3SUM problem Started with BRUTE-FORCE → checked every triplet. 😀 Worked 😇 but SLOW for big arrays (O(n³)) → TIME LIMIT EXCEEDED. Faced errors along the way: 'int object not iterable' → I wrote sorted(a,b,c) instead of sorted([a,b,c]). 'unhashable type: list' → Tried adding list to set. Fixed by converting to tuple. LOGICAL BUG → Return inside the loop returned early. Fixed by moving return outside. Finally moved to OPTIMAL TWO-POINTER APPROACH: Sort array first. Use two pointers to find pairs for target -nums[i]. Skip duplicates carefully. Complexity reduced to O(n²). 💡 Lessons learned: small syntax mistakes can cause big errors, immutable types are key for sets, and proper pointer logic makes code efficient. #Python #Algorithms #LeetCode #ProblemSolving #CodingJourney

𝗗𝗮𝘆 𝟯𝟵 𝗼𝗳 #𝟭𝟴𝟬𝗗𝗮𝘆𝘀𝗢𝗳𝗖𝗼𝗱𝗲 Today, I built on the first/last occurrence solution to 𝗰𝗼𝘂𝗻𝘁 𝗼𝗰𝗰𝘂𝗿𝗿𝗲𝗻𝗰𝗲𝘀 𝗼𝗳 𝗮 𝘁𝗮𝗿𝗴𝗲𝘁 𝗶𝗻 𝗮 𝘀𝗼𝗿𝘁𝗲𝗱 𝗮𝗿𝗿𝗮𝘆 𝘄𝗶𝘁𝗵 𝗱𝘂𝗽𝗹𝗶𝗰𝗮𝘁𝗲𝘀. Using the same lower_bound and upper_bound helpers: Lower bound → first index where element ≥ target Upper bound → first index where element > target The count is simply: count = upper_bound - lower_bound This gives an O(log n) solution — much faster than scanning the entire array, especially with many duplicates. It’s a great example of how breaking a problem into reusable pieces leads to clean and efficient code. Perfect for analytics, frequency analysis, and search optimizations! 📊 #Python #Algorithms #BinarySearch #FrequencyCount #Coding #ProblemSolving

🚀 LeetCode #1625: Lexicographically Smallest String After Applying Operations Today’s problem was about transforming a numeric string using two operations: adding a value to digits at odd indices and rotating the string, to get the lexicographically smallest result possible. The challenge was to handle infinite possibilities smartly. I used a Breadth First Search (BFS) approach to systematically explore all reachable string states while keeping track of visited ones. 💡 Key Takeaways: - Some problems don’t need a direct formula, they need systematic exploration. - BFS is not just for graphs; it’s a powerful tool for exploring state transitions too. - Modular arithmetic and rotation logic often come together in string manipulation problems. This one was a great reminder that clean logic and state tracking can solve even the most “infinite looking” problems efficiently. #LeetCode #ProblemSolving #Python #DSA #CodingChallenge #Algorithms #BFS #StringManipulation #LearningEveryday

Day 16 of #100DaysOfLeetCode Today’s problem focused on substring counting within binary strings and required an efficient approach to handle potentially large input sizes without generating every substring explicitly. 1. Number of Substrings With Only 1s The task was to count the total number of substrings that consist entirely of the character '1', with the final result taken modulo (10^9 + 7). Instead of constructing the substrings, the key insight is that each continuous block of 1s contributes a predictable number of valid substrings. 🔹 My Approach: Iterated through the string while tracking the current streak length of consecutive 1s. Each time a block ended, computed the number of substrings from that block using the formula: k*(k+1)/2 where k is the length of the streak. Added the total from each block to the final answer, applying the modulo constraint throughout. Completed the process with a final update for any trailing block of 1s. What I Learned: This problem reinforces how recognizing mathematical patterns within sequences can transform a brute-force solution into a simple linear scan. Efficient substring counting often comes down to understanding structure rather than enumerating possibilities. 📊 Complexity Analysis: Time Complexity: O(n) — single pass over the string. Space Complexity: O(1) — constant space approach. #day16 #100daysofleetcode #leetcode #DSA #python #leetcodes #striver

Day 68: Search in 2D Sorted Matrix (Search Space Reduction) 🔎 I'm continuing the streak on Day 68 of #100DaysOfCode with a challenging matrix search problem! The task is to find a target value in an $m \times n$ matrix where both rows and columns are sorted in ascending order. The key to solving this efficiently is Search Space Reduction. Instead of performing a standard search, my solution uses a smart traversal technique: Starting Point: I begin the search at the top-right corner of the matrix. Decision Logic: If the current value equals the target, we stop. If the current value is greater than the target, the entire current column can be eliminated, so we move left. If the current value is less than the target, the entire current row can be eliminated, so we move down. This strategy eliminates one row or one column in every step, guaranteeing an optimal O(m + n) time complexity and O(1) extra space. #Python #DSA #Algorithms #Matrix #Search #100DaysOfCode #ProblemSolving