Solved LeetCode 901 Online Stock Span in Java with Monotonic Stack

🚀 Day 48 of My #LeetCode Journey Today’s problem: 2615. Sum of Distances 💡 Key Idea: Instead of calculating distances between equal elements using brute force (O(n²)), I used: HashMap to group indices of same values Prefix Sum to efficiently compute distances This reduced the complexity to O(n) 🔥 🧠 What I Learned: How prefix sums can optimize distance calculations Efficient handling of repeated elements Writing clean and optimized code using Java ⚡ Approach: Store indices of each number Use prefix sums to calculate left & right distances Combine both to get final answer 📈 Time Complexity: O(n) 📦 Space Complexity: O(n) Consistency is key. Small progress every day leads to big results 💪 #Day48 #Java #FullStackDeveloper #CodingJourney #100DaysOfCode #DSA #LeetCode

Day 97 - LeetCode Journey Solved LeetCode 496: Next Greater Element I in Java ✅ This is a perfect example of combining Monotonic Stack + HashMap for efficiency. Instead of checking each element one by one, I precomputed the next greater elements using a stack and stored them in a map for quick lookup. Smart preprocessing saves time 💡 Key idea: Traverse nums2, use a stack to find next greater elements, and map them for instant access. Key takeaways: • Monotonic Stack pattern • Using HashMap for fast queries • Avoiding nested loops (O(n²) → O(n)) • Preprocessing for optimization ✅ All test cases passed ⚡ O(n) time and O(n) space Stack + Map combo is a game changer for these types of problems 🔥 #LeetCode #DSA #Java #Stack #MonotonicStack #HashMap #ProblemSolving #CodingJourney #InterviewPrep #Consistency #100DaysOfCode

Day 93 - LeetCode Journey Solved LeetCode 9: Palindrome Number in Java ✅ At first glance, it feels like a string problem… but the real challenge is solving it without converting to string. Instead of reversing the whole number, I reversed only half of it and compared both parts. This avoids overflow and keeps it efficient. Smart approach > brute force 💡 Key takeaways: • Handling edge cases (negative numbers, trailing zeroes) • Reversing only half of the number • Avoiding extra space (no string conversion) • Writing optimized mathematical logic ✅ All test cases passed ⚡ O(log n) time and O(1) space Sometimes the best solutions are the simplest ones, just a different way of thinking 🔥 #LeetCode #DSA #Java #Math #ProblemSolving #CodingJourney #InterviewPrep #Consistency #100DaysOfCode

🚀 Day 27/100 Days of Code Challenge Today’s problem: Find Peak Element (Leetcode 162) 🔍 What I learned: How to find a peak element efficiently without scanning the entire array Using Binary Search to reduce time complexity from O(n) to O(log n) Understanding how the “slope” of elements helps decide the search direction 🧠 Key Idea: Instead of checking every element, compare the middle element with its neighbor: If nums[mid] < nums[mid + 1] → move right Else → move left ✅ Example: Input: [1, 2, 3, 1] Output: 2 (index of peak element 3) Consistency is key 🔑 — improving problem-solving skills one day at a time! 💪 #Day27 #100DaysOfCode #LeetCode #BinarySearch #DSA #Java #CodingJourney

Day 94 - LeetCode Journey Solved LeetCode 35: Search Insert Position in Java ✅ Classic Binary Search problem that tests your fundamentals. Instead of just finding the element, the twist is to return the correct insert position if it’s not present. The key idea is simple: keep narrowing the search space and finally return low, which represents the right position. Clean logic, high impact 💡 Key takeaways: • Strong grip on Binary Search fundamentals • Understanding search space boundaries • Returning correct insertion index • Writing efficient O(log n) solutions ✅ All test cases passed ⚡ O(log n) time and O(1) space Mastering basics like Binary Search is what builds real problem-solving strength 🔥 #LeetCode #DSA #Java #BinarySearch #ProblemSolving #CodingJourney #InterviewPrep #Consistency #100DaysOfCode

🚀 Day 65/180 | #180DaysOfCode 📍 LeetCode | 💻 Java Solved: 2535. Difference Between Element Sum and Digit Sum of an Array Used a single loop + digit extraction approach to calculate both element sum and digit sum efficiently. ⏱️ Time Complexity: O(n × d) 📦 Space Complexity: O(1) Strengthening understanding of number manipulation and digit-based operations. 💪 Consistency continues 🚀 #DSA #LeetCode #Java #CodingJourney #Consistency

Day 92 of #100DaysOfLeetCode 💻✅ Solved #739. Daily Temperatures problem in Java. Approach: • Used Monotonic Stack to track indices • Compared current temperature with stack top • Updated result when a warmer day was found • Stored indices for future comparisons Performance: ✓ Runtime: 60 ms (Beats 79.01% submissions) 🚀 ✓ Memory: 107.89 MB (Beats 17.53% submissions) Key Learning: ✓ Learned Monotonic Stack technique ✓ Improved handling of next greater element problems ✓ Strengthened stack-based problem solving Learning one problem every single day 🚀 #Java #LeetCode #DSA #Stack #Arrays #ProblemSolving #CodingJourney #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 29/100 – #100DaysOfCode Today’s problem: Middle of the Linked List (LeetCode 876) 🎯 💡 What I learned: How to find the middle node efficiently using the two-pointer (slow & fast) approach Understanding why the fast pointer moves twice as fast as the slow pointer Handling both odd and even length linked lists Writing optimal code with O(n) time and O(1) space 🧠 Key Idea: Use two pointers: slow → moves 1 step at a time fast → moves 2 steps at a time 👉 When fast reaches the end, slow will be at the middle! 📊 Complexity: Time: O(n) Space: O(1) 📈 One step closer to mastering Linked Lists..... #Day29 #100DaysOfCode #LeetCode #LinkedList #DSA #Java #CodingJourney #ProblemSolving #TechSkills

Day 32 of #50DaysLeetCode Challenge 💻🔥 Today I solved the “Rotate Image” problem using Java. 🔹 Problem: Given an n × n matrix, rotate the image 90° clockwise in-place (no extra matrix allowed). 🔹 Where people mess up: Trying to simulate rotation directly with extra space. That defeats the whole point of the problem. 🔹 Optimal Approach: 1. Transpose the matrix (swap rows & columns) 2. Reverse each row That’s it. Two clean steps. No overthinking. 🔹 Key Insight: Rotation isn’t magic — it’s just a combination of simple transformations. 🔹 Time Complexity: O(n²) 🔹 Space Complexity: O(1) 📌 What I learned: Most matrix problems look complicated until you break them into small predictable operations. If your approach feels messy, you’re probably doing it wrong. Simple > Clever. #Day32#LeetCode #Java #Matrix #DSA #CodingChallenge #ProblemSolving