An authentication system to keep your app secure and user-friendly with:. User registration & login.Route protection.Password reset via OTP.Email verification .Access protected content via “Get Started”.Try the demo: #mern #Authentication #LearnInPublic.

LeetCode 1614 – Maximum Nesting Depth of Parentheses. Solved: Find max depth of nested parentheses.Traverse string, increment on '(',decrement on ')'.Track maximum depth reached.O(n) time, O(1)space.Simple yet useful stack-like logic!. #LeetCode #100DaysOfCode #PythonDSA #Strings.

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LeetCode 8 – String to Integer (atoi). Solved: Convert string to 32-bit signed integer.Steps:.Ignore leading spaces.Handle sign + / -.Build number till non-digit.Clamp to integer range.Classic string parsing problem!. #LeetCode #100DaysOfCode #PythonDSA #Strings #DSA.

LeetCode 451 – Sort Characters By Frequency. Solved: Sort string chars by decreasing frequency.Count freq with hashmap → sort by count → rebuild string.O(n log n) time, O(n) space.Great practice for hashmaps + sorting!. #LeetCode #100DaysOfCode #HashMap #PythonDSA #Strings.

LeetCode 796 – Rotate String. Solved: Check if one string is rotation of another.Trick: s2 must be a substring of s1 + s1.Simple check with in operator.O(n²) worst-case, O(1) extra space.Neat and elegant string trick!. #LeetCode #100DaysOfCode #PythonDSA #Strings #DSA.

LeetCode 205 – Isomorphic Strings.Solved: Check if two strings follow the same pattern.Used two hash maps to track character mappings both ways.Ensures one-to-one mapping between characters.O(n) time, O(1) space (fixed alphabet). #LeetCode #100DaysOfCode #HashMap #PythonDSA #DSA.

LeetCode 540 – Single Element in a Sorted Array. Find element that appears once in sorted array.Binary search with index parity logic.Pairs start at even index before single element.Shift search space based on mid’s pairing.O(log n) time, O(1) space. #BinarySearch #DSA #PythonDSA.

LeetCode 153 – Find Minimum in Rotated Sorted Array. Solved: Find smallest element in rotated sorted array.Used binary search.Compared mid with right to decide search side.O(log n) time, O(1) space.Elegant and efficient!. #LeetCode #100DaysOfCode #BinarySearch #DSA #PythonDSA.

LeetCode 162 – Find Peak Element. Solved: Find index of any peak element.Binary search approach.If nums[mid] < nums[mid+1] → go right, else go left.O(log n) time, O(1) space.Clean divide-and-conquer trick!. #LeetCode #100DaysOfCode #BinarySearch #DSA #PythonDSA.

Authentication Update. Built & styled frontend pages.Integrated frontend with backend APIs.Implemented email verification system:.Send OTP to user’s email.Verify OTP and update account status. Secure & smooth auth flow live!. #MERN #ReactJS #NodeJS #DevConnect #FullStackDeveloper.

LeetCode 81 – Search in Rotated Sorted Array II. Solved: Like LC33 but with duplicates.Modified Binary Search.Skip duplicates if nums[left] == nums[mid] == nums[right].Still O(log n) in best case, O(n) worst case due to duplicates.#LeetCode #100DaysOfCode #PythonDSA #BinarySearch.

LeetCode 33 – Search in Rotated Sorted Array. Solved: Find target in rotated sorted array.Applied modified binary search.Checked which half is sorted, then narrowed down.Time Complexity: O(log n).Tricky but powerful once mastered!.#LeetCode #100DaysOfCode #BinarySearch #PythonDSA.

Progress Update - Auth System. Implemented Password Reset Flow with:.OTP verification via email .Secure password update after OTP validation. Fetched User Data with:.Verified user details.Account verification status included. #MERN #NodeJS #JWT #Nodemailer #FullStack.

LeetCode 34 –First and Last Position of Element in Sorted Array.Solved: Find starting and ending position of a target in a sorted array.Binary search twice:once for left bound, once for right.Handles duplicates efficiently.Refined binary logic at its best!.#LeetCode #BinarySearch.

Email + OTP Verification !. Just integrated Nodemailer app to:.Send welcome emails after registration.Deliver OTPs for secure email verification.Built custom routes + middleware for OTP auth flow. Clean, scalable, and secure! . #MERN #NodeJS #Nodemailer #BackendDevelopment.

LeetCode 35 – Search Insert Position. Solved: Find index to insert target in sorted array.Binary search to locate or find insert spot.Useful in auto-sorted data structures.Quick win with binary intuition!. #100DaysOfCode #LeetCode #BinarySearch #PythonDSA.

LeetCode 704 – Binary Search. Solved: Classic binary search on sorted array.Kept adjusting low, high till target found or not.Time complexity: O(log n).Foundations of efficient search algorithms!. #LeetCode #PythonDSA #100DaysOfCode #BinarySearch.

Just finished building user authentication with the MERN stack!.Today I implemented:.User registration.Secure login/logout.Organized auth controllers & routes in Express. Learned a lot about structuring backend logic +working with JWTs. #MERN #NodeJS #MongoDB #express #DevJourney.

LeetCode 54 – Spiral Matrix. Solved: Return all elements of a matrix in spiral order.Used boundaries: top, bottom, left, right.Moved layer by layer inward while collecting elements.Great for mastering 2D traversal logic!. #100DaysOfCode #LeetCode #PythonDSA #MatrixProblems.

LeetCode 560 – Subarray Sum Equals K. Solved: Count subarrays whose sum equals k.Brute: O(n²) with prefix sums.Optimal: O(n) using hashmap + prefix sum.Powerful combo of hashing & prefix logic!. #LeetCode #100DaysOfCode #PythonDSA #PrefixSum #HashMap.