Single Element in Sorted Array Binary Search

Day 57/100 | #100DaysOfDSA ⛰️🔍 Today’s problem: Peak Index in a Mountain Array A perfect use-case of Binary Search on a pattern. Key observation: The array increases → reaches a peak → then decreases. Approach: • Use binary search on the index • Compare mid with mid + 1 • If arr[mid] > arr[mid + 1] → we are on the decreasing side → move left • Else → we are on the increasing side → move right This guarantees we always move toward the peak. Time Complexity: O(log n) Space Complexity: O(1) Big takeaway: Binary search isn’t just for sorted arrays — it works on patterns too. Recognizing these patterns is a game changer. 🔥 Day 57 done. #100DaysOfCode #LeetCode #DSA #Algorithms #BinarySearch #Arrays #Java #CodingJourney #ProblemSolving #InterviewPrep #TechCommunity

Day 58/100 | #100DaysOfDSA 🔄🔍 Today’s problem: Search in Rotated Sorted Array A twist on Binary Search with a rotated array. Key idea: Even though the array is rotated, one half is always sorted. Approach: • Use binary search • Find mid element • Check which half is sorted (left or right) • Decide if target lies in the sorted half • Narrow the search accordingly Why it works: At every step, we eliminate half of the search space just like standard binary search. Time Complexity: O(log n) Space Complexity: O(1) Big takeaway: Understanding the structure of the problem helps adapt classic algorithms like binary search. Rotation doesn’t break order — it just shifts it. 🔥 Day 58 done. #100DaysOfCode #LeetCode #DSA #Algorithms #BinarySearch #Arrays #Java #CodingJourney #ProblemSolving #InterviewPrep #TechCommunity

Day 61/100 | #100DaysOfDSA 🧩🚀 Today’s problem: Median of Two Sorted Arrays A classic hard problem with a clever binary search approach. Problem idea: Find the median of two sorted arrays without fully merging them. Key idea: Use binary search on the smaller array to partition both arrays. Why? • We want left half and right half to be balanced • All elements in left ≤ all elements in right How it works: • Pick a cut in array1 • Derive cut in array2 • Check partition validity using boundary elements If valid → we found the median If not → adjust the partition Time Complexity: O(log(min(m, n))) Space Complexity: O(1) Big takeaway: Binary search isn’t just for searching — it can be used to optimize partitions and positions. This one really builds intuition. 🔥 Day 61 done. #100DaysOfCode #LeetCode #DSA #Algorithms #BinarySearch #Java #CodingJourney #ProblemSolving #InterviewPrep #TechCommunity

#100DaysOfCode – Day 2 Today I worked on a DSA problem based on arrays: Check if an array is sorted and rotated 🔍 Approach: Instead of finding the exact rotation point, I focused on identifying a pattern: In a sorted and rotated array, the order should break at most once. So, I checked how many times an element is greater than the next element while traversing the array in a circular manner. ✔️ If the count of such breaks is 0 or 1 → valid ❌ If it’s more than 1 → not a sorted rotated array 🧠 Key Takeaway: This problem taught me how pattern observation can simplify logic and avoid unnecessary complexity. Sometimes the best solution is not the most obvious one! 📈 Staying consistent and improving step by step 💪 #100DaysOfCode #DSA #DataStructures #Algorithms #Java #CodingJourney #ProblemSolving #LeetCode #Consistency

📘 DSA Journey — Day 35 Today’s focus: Binary Search with index patterns. Problem solved: • Single Element in a Sorted Array (LeetCode 540) Concepts used: • Binary Search • Index parity (even/odd pattern) • Search space reduction Key takeaway: The array is sorted and every element appears twice except one. A key observation: Before the single element, pairs start at even indices After the single element, this pattern breaks. Using binary search: • If mid is even and nums[mid] == nums[mid + 1], the single element lies on the right side • Else, it lies on the left side (including mid) By leveraging this pattern, we can find the answer in O(log n) time and O(1) space. Continuing to strengthen binary search intuition and consistency in problem solving. #DSA #Java #LeetCode #CodingJourney

Day 56/100 | #100DaysOfDSA 🧠⚡ Today’s problem: String Compression A clean in-place array manipulation problem. Core idea: Compress consecutive repeating characters and store the result in the same array. Approach: • Traverse the array using a pointer • Count consecutive occurrences of each character • Write the character to the array • If count > 1 → write its digits one by one • Move forward and repeat Key insight: We don’t need extra space — just carefully manage read & write pointers. Time Complexity: O(n) Space Complexity: O(1) Big takeaway: In-place algorithms require precise pointer control but give optimal space efficiency. Mastering these improves real-world memory optimization skills. 🔥 Day 56 done. #100DaysOfCode #LeetCode #DSA #Algorithms #Strings #TwoPointers #InPlace #Java #CodingJourney #ProblemSolving #InterviewPrep #TechCommunity

Day 79/100 | #100DaysOfDSA 🧩🚀 Today’s problem: Flatten Binary Tree to Linked List A powerful tree transformation problem using pointer manipulation. Problem idea: Convert a binary tree into a linked list in-place following preorder traversal. Key idea: Iterative traversal + rewiring (similar to Morris traversal idea). Why? • We need preorder sequence (Root → Left → Right) • Instead of extra space, we modify pointers in-place • Efficient and avoids recursion stack How it works: • Traverse using a pointer curr • If left child exists: → Find rightmost node of left subtree → Connect it to current’s right subtree → Move left subtree to right → Set left = null • Move to next node (curr.right) Time Complexity: O(n) Space Complexity: O(1) Big takeaway: Tree problems can often be optimized using in-place pointer rewiring, avoiding extra space. 🔥 This pattern is very useful for tree flattening and traversal optimizations. Day 79 done. 🚀 #100DaysOfCode #LeetCode #DSA #Algorithms #BinaryTree #MorrisTraversal #Java #CodingJourney #ProblemSolving #InterviewPrep #TechCommunity

Day 2/30 — DSA Challenge 🚀 Problem: Lowest Common Ancestor of Deepest Leaves Topic: Tree + DFS Difficulty: Medium Approach: Used DFS to calculate depth of left and right subtrees At each node, compared depths: If equal → current node is LCA Else → return deeper subtree result Mistake / Challenge: Initially overcomplicated thinking about storing all deepest nodes Realized we don’t need to track nodes explicitly, depth comparison is enough Fix: Returned a Pair (node, depth) from recursion Handled everything in one DFS traversal Key Learning: Tree problems often look complex but can be simplified with recursion Focus on what needs to be returned from each call Time Taken: 60 minutes Consistency check ✅ See you on Day 3. GitHub Repo: https://lnkd.in/g87geK_g #DSA #LeetCode #Java #Trees #Recursion #LearningInPublic

Day 70 of My DSA Journey Problem: Linked List Cycle (LeetCode 141) Today’s problem was all about detecting whether a linked list contains a cycle — a classic and very important concept in data structures. Key Idea: Floyd’s Cycle Detection Algorithm (Tortoise & Hare) Instead of using extra memory, we use two pointers: • Slow pointer → moves 1 step • Fast pointer → moves 2 steps If there’s a cycle, these two pointers will eventually meet. If not, the fast pointer will reach the end (null). Insight: This approach is efficient because it avoids using extra space like a HashSet and still guarantees detection in linear time. Complexity: • Time: O(n) • Space: O(1) What I learned: Sometimes, the smartest solutions don’t require extra space — just a clever observation and pointer manipulation! Consistency > Perfection 💯 On to Day 71 🚀 #DSA #100DaysOfCode #Java #CodingJourney #ProblemSolving #LinkedList

🔥 Day 63 of #100DaysOfCode Solved – Missing Number 🔍 What I did: Calculated the expected sum of numbers from 0 to n and subtracted the actual sum of the array to find the missing number efficiently. 💡 Key Learning: Learned how to use mathematical formula (n × (n+1) / 2) Practiced optimizing from brute force to O(n) solution Improved understanding of number patterns in arrays 🎯 Takeaway: Using mathematical insights can simplify problems and eliminate the need for extra loops or space. #Day62 #LeetCode #Java #ProblemSolving #CodingJourney #100DaysOfCode #DSA