🪐 Leetcode DS & Algo Resources

Data Structures and Algorithms in Real Life !!! Array : 2D arrays (matrices) are mainly used in Image Processing. RGB image uses a 3D matrix. 2D arrays are also used in Game Design like Sudoku, Chess. The Leader Board of game or coding contest. Stack : Used in backtracking, check valid parenthesis in an expression. Evaluating Infix and Postfix expressions. Used in Recursive function calls to store function calls and their results. Undo and Redo operations in word processors like MS-Word, and Notepad. Browsing history of visited websites. Call history/log in mobile phones. Java Virtual Machine uses a stack to store immediate calculation results. Queue : Windows operating system uses a circular queue to switch between different applications. Used in First Come First Serve job/CPU scheduling algorithm which follows FIFO order. All the requests are queued for the server to respond. Priority Queue : A priority queue is used in priority scheduling algorithm and interrupt handling in OS. Used in Huffman Coding in compression algorithms. Linked List : Previous and Next Page in Web Browser. Songs in the music player are linked to the previous and next songs using doubly linked list. Next and previous images in a phone gallery. Multiple Applications running on a PC uses circular linked list. Used for the implementation of stacks, queues, trees, and graphs. Graph : In Facebook, LinkedIn and other social networking sites, users are considered to be the vertices and the edge between them indicates that they are connected. Facebook’s Graph API and Google’s Knowledge API are the best examples of grpah. Google Maps, Yahoo Maps, Apple Maps uses graph to show the shortest path using Breadth First Search (BFS). Used in HTML DOM and React Virtual DOM. Tree : Representation structure in File Explorer. (Folders and Subfolders) uses N-ary Tree. Auto-suggestions when you google something using Trie. Used in decision-based machine learning algorithms. Used in Backtracking to maintain the state-space tree. A binary tree is used in database indexing to store and retrieve data in an efficient manner. To implement Heap data structure. Binary Search Trees (BST) can be used in sorting algorithms. Dijkstra Algorithm : This algorithm is used to find the shortest path between two vertices in a graph in such a way that the sum of weights between the edges is minimum. Prims Algorithm : It is a greedy algorithm to obtain a minimum spanning tree.

5 things that improved logic. 1. I used pen and paper to understand everything. I had less visualising power, so whatever I did not understand, I used to go in-depth using pen and paper only. It worked really well for me. 2. I used to do healthy discussions with my 2-3 friends on problems. Something is there that you actually learn a lot from others. Those discussions gave me a new thought process and eventually improved my logic. 3. I continuously used to revise any new concepts which I had learnt earlier. Some things did not go in mind the first time, but as you revise it 4-5 times, it starts going into your mind and help to build your logic. 4. I always had an attitude to learn. So even if I could solve a particular problem, I used to see solutions from others. That really helped me in an overall improvement in logic, and I was able to apply similar logic in new problems. 5. I always knew logical thinking would play a critical role throughout my life. No one is best in logic. It's just that logic can only be improved. So I focussed on improvement rather than focussing on becoming the best. Credits: Unknown.

Graph notes. https://noi.ph/training/weekly/week2.pdf?x75983

- DSA Topic-wise Roadmaps along with questions to be solved. - Coding patterns and techniques are explained in graphic format. https://www.instagram.com/thriverashish/

Striver’s DP notes. https://www.linkedin.com/posts/raushankumar43_striver-dynamic-programming-notes-activity-6947868592293978112-HvPk?utm_source=linkedin_share&utm_medium=ios_app

𝐂𝐨𝐦𝐩𝐥𝐞𝐭𝐞 𝐃𝐒𝐀 𝐑𝐨𝐚𝐝𝐌𝐚𝐩 (𝐅𝐢𝐫𝐬𝐭 30 𝐃𝐚𝐲𝐬) 🎯 𝐀𝐫𝐫𝐚𝐲𝐬  📌 Day 1 📔Understand Big O notation 📌 Day 2 📔Study Basic Concepts of Array 📔 Reverse the array in place 📌 Day 3 and Day4 📔 Understand Sorting 📔 Implement them all in your fav programming language 📌 Day 5 📔 Understand Binary Search Algorithm 📔 Search an element in Sorted Array 📔 https://lnkd.in/dcXDGjJb 📔  https://lnkd.in/d8XnAp22 📌 Day 6 📔Understand 2D matrix/ @D Arrays 📔Search a 2D Matrix https://lnkd.in/db7cGdez 📔 Set Matrix to Zer https://lnkd.in/dV3gUPEf 📔 Pascals Triangle https://lnkd.in/dCrmGNby 📔 Rotate Matrix https://lnkd.in/d7wkU8UV 📌 Day 7 & 8 📔 Kadane’s Algo  https://lnkd.in/dJ2X9gzw 📔 Sort Array of 0’s 1’s and 2’s https://lnkd.in/dNWw6Bp8 📔 Two Sum Problem  https://lnkd.in/dqsSyqBB 📔 Find Duplicate  https://lnkd.in/dMdz7KXq 📔Stock Buy and Sell  https://lnkd.in/dGv_8HUE 📔 Next Permutation https://lnkd.in/dNfymKti 📔 Merge Intervals https://lnkd.in/dxbbt7wF 📔Merge Sorted Arrays https://lnkd.in/dNzpA3eU 📌 Day 9 & 10 📔Reverse pairs —> https://lnkd.in/d7erN9PU 📔 Grid Unique Paths —> https://lnkd.in/dUS3mxaS 📔 3 Sum problem --> https://lnkd.in/djjGS4ep 📔 4 Sum Problem —> https://lnkd.in/dtKJ-a5K 📔Repeat Missing Number Array 📔 Reverse Pairs 📔 Longest Consecutive Subsequence 📔 Subarray with given Xor  𝐋𝐢𝐧𝐤𝐞𝐝𝐋𝐢𝐬𝐭  📌 Day 11 & 12 📔Understand the concept 📔Understand its Advantages 📔Implement Linked list 📔Reverse Linked List 📔Find the Middle 📔Remove Nth Node 📔Merge Two Sorted Lists 📌 Day 13 📔Add Two Numbers given in linked list 📔Detect and remove Linked List Cycle 📔Intersection of Two Linked Lists 📌 Day 14 📔Reverse Nodes in k-Group 📔Rotate List 📔Flattening a Linked List 📔Copy List with Random Pointer 𝐒𝐓𝐀𝐂𝐊  📌 Day 15 📔Understand the basics 📔Relate real-life examples like  📔Implement the Stack using Arrays (Push Pop etc functionalities ) 📔Implement the Stack with Linked List 📌 Day 16 📔Sort a Stack 📔Valid Parenthesis: 📔Retrieve Minimum Element 📌 Day 17 (Level Up) 📔Next Greater Element using Stack 𝐐𝐔𝐄𝐔𝐄  📌 𝐃𝐚𝐲 18 📔 Understand the basics of Queue Data Structures 📔 Relate with some real-life examples 📔 Implement the Queue using Arrays 📔 Implement the Queue using Linked List 📌 𝐃𝐚𝐲 19 📔 Implement Queue using Stack 📔 Implement Stack using Queue 📔 Implement and understand Double Ended Queue 📌 𝐃𝐚𝐲 20 📔 Understand and Implement Circular Queue 📔 Fine examples where circular Queues can be used. 📔 Implement Producer-Consumer Problem 📌 𝐃𝐚𝐲 21 📔 Queue Reversal 📔 Implement LRU, LFU Cache 📌 𝐃𝐚𝐲 22 📔 Learn Sliding window Pattern 📔 Sliding Window Maximum LC 239 📔 First negative integer in every window of size 📌 𝐃𝐚𝐲 23 📔 Trapping Rain Water 📔 Simplify Directory 𝐑𝐞𝐜𝐮𝐫𝐬𝐢𝐨𝐧 📌 𝐃𝐚𝐲 24 and 25 📗Understand Recursion 📗Fibonacci Number 📌 𝐃𝐚𝐲 26 & 27 📗Subset Sums 📗Subsets II 📗Combination Sum 📌 𝐃𝐚𝐲 28-30 Revision

All DSA sheets links: Apna college 375 Qs DSA sheet https://docs.google.com/spreadsheets/u/0/d/1hXserPuxVoWMG9Hs7y8wVdRCJTcj3xMBAEYUOXQ5Xag/htmlview Love Babbar 450 Qs DSA sheet https://drive.google.com/file/d/1FMdN_OCfOI0iAeDlqswCiC2DZzD4nPsb/view Striver 180 Qs DSA sheet https://takeuforward.org/interviews/strivers-sde-sheet-top-coding-interview-problems/ Siddharth Singh 450 Qs DSA Sheet https://docs.google.com/spreadsheets/u/0/d/11tevcTIBQsIvRKIZLbSzCeN4mCO6wD4O5meyrAIfSXw/htmlview LeadCoding by Fraz 250 Qs DSA Sheet https://docs.google.com/spreadsheets/u/0/d/1-wKcV99KtO91dXdPkwmXGTdtyxAfk1mbPXQg81R9sFE/htmlview Arsh Goyal 280 Qs DSA Sheet https://docs.google.com/spreadsheets/d/1MGVBJ8HkRbCnU6EQASjJKCqQE8BWng4qgL0n3vCVOxE/htmlview?usp=sharing&pru=AAABgKkdtIE*rPv8dPkWyOpfwjprKvKSeA The Code Skool DSA Sheet https://docs.google.com/document/u/0/d/1RxKKXJtErQFJjMfAh1kV-DyQsZoiESayimFx6PPIhVE/mobilebasic

DSA sheet by ARSH. https://docs.google.com/spreadsheets/d/1MGVBJ8HkRbCnU6EQASjJKCqQE8BWng4qgL0n3vCVOxE/htmlview?usp=sharing&pru=AAABgKkdtIE*rPv8dPkWyOpfwjprKvKSeA

250 DSA problem sheet by FRAZ. https://docs.google.com/spreadsheets/u/0/d/1-wKcV99KtO91dXdPkwmXGTdtyxAfk1mbPXQg81R9sFE/htmlview

50 Beginner DSA problems by FRAZ. https://docs.google.com/spreadsheets/d/1rKzW_Gtrxv6eS3W4YGDFFFDmOaB2XXRJBpkXe9qJHsM/edit?usp=sharing