resources
A second teacher, for every chapter
Sometimes another voice makes it click. These are hand-picked and link-checked, one to three per chapter, with the language always labelled. Filter by language or kind.
111 resources
Java for DSA
01 · Java Memory
- ▶ videoIntroduction to Programming - Types of Languages, Memory Management ↗Kunal Kushwaha · EnglishDraws the stack, the heap and the reference arrow between them, so you can see what
newreally does before arrays and objects get shared. - ◈ visualizerVisualize Java Code - Java Visualizer, Tutor, and Debugger ↗Python Tutor (Philip Guo) · EnglishPaste a small Java program and step through it line by line, watching stack frames and heap objects appear. It's the fastest way to check your mental picture.
- ✎ articleStack Memory and Heap Space in Java ↗Baeldung · EnglishA short read on what lives where, with a worked example, plus why StackOverflowError and OutOfMemoryError are two different problems.
02 · Java Arrays & Strings
- ▶ videoIntroduction to Arrays and ArrayList in Java ↗Kunal Kushwaha · EnglishArrays and ArrayList from zero: memory, 2D arrays, how a dynamic array grows, and arrays passed into functions, with questions solved along the way.
- ▶ videoStrings and StringBuilder in Java ↗Kunal Kushwaha · EnglishHow Java strings work inside: the pool, immutability and memory. Once you see why
+=in a loop is slow, StringBuilder makes sense. - ▶ videoLecture 14: Strings in Java || DSA Series by Babbar ↗Love Babbar (CodeHelp) · HindiJava strings in Hindi, from a Java series built for DSA, with written notes linked. Watch this if Kunal's pace feels fast.
03 · Java OOP
- ▶ playlistObject Oriented Programming (OOP) in Java Course ↗Kunal Kushwaha · EnglishSeven lectures, from classes and constructors to interfaces, generics, lambdas and the Collections Framework. This is the OOP a DSA coder uses every day.
- ▶ videoJava OOPs in One Shot | Object Oriented Programming | Java Language | Placement Course ↗Apna College · HindiJava OOP in one sitting, in Hindi. Good for a quick revision of classes, objects and the four pillars before a round.
- § docsObject as a Superclass ↗Oracle · The Java Tutorials · EnglishThe official word on equals(), hashCode() and toString(). Your own class must follow this contract before it can work as a HashMap key.
04 · I/O & Debugging
- ✎ articleFast Input & Output ↗USACO Guide · EnglishWhy Scanner can time out on big inputs, and how BufferedReader, StringTokenizer and PrintWriter fix it. The Java templates are ready to copy.
- § docsTutorial: Debug your first Java application ↗JetBrains · IntelliJ IDEA docs · EnglishBreakpoints, stepping and watching variables, step by step. Learn it once and you can use it on every wrong answer.
- ▶ videoHow To Debug Your Code | How To Solve Any Coding Problem In Your Interview Part 3 ↗Aditya Verma · HindiHow to find your own bug calmly when there's no debugger, which is the usual situation in an interview.
05 · Java Toolkit
- ▶ playlistJava Collections Framework Complete Course 2026 | From Zero to Professional ↗Engineering Digest · HindiThe whole Collections Framework in Hindi, one class per video: ArrayList, HashMap, TreeMap, sets, queues, Comparable and Comparator.
- § docsTrail: Collections ↗Oracle · The Java Tutorials · EnglishOracle's own tour of the collection interfaces, implementations and algorithms. Come back to it whenever you forget which class to use.
- ✎ articleThe Java HashMap Under the Hood ↗Baeldung · EnglishWhat really happens on put() and get(): buckets, collisions, load factor, rehashing, and the Java 8 switch to trees. Interviewers like to ask about these internals.
Thinking tools
06 · Mindset
- ▶ playlistInterview 101 | How to approach any Coding problem ↗Aditya Verma · HindiThree honest talks on facing an unseen problem: managing time, reading the constraints, and debugging. It's the same routine this chapter builds.
- ▶ videoHow to: Work at Google — Example Coding/Engineering Interview ↗Life at Google · EnglishGoogle's own mock interview. The candidate asks questions, starts from the quadratic solution and improves it out loud. Those are the habits being scored.
- ✎ articleCoding interview cheatsheet: Best practices before, during and after ↗Tech Interview Handbook (Yangshun Tay) · EnglishA one-page checklist for before, during and after a coding round. Reread it the night before.
07 · Big-O
- ▶ videoTime and Space Complexity COMPLETE Tutorial - What is Big O? ↗Kunal Kushwaha · EnglishA long, careful tour of Big-O, Omega and Theta, recurrences, and the cost of recursive code. Watch it in parts; every later chapter uses it.
- ▶ videoTime and Space Complexity - Strivers A2Z DSA Course ↗Striver (take U forward) · EnglishShort and practical: counting steps, why constants drop, worst vs average case, and the time limits judges actually use.
- ▶ videoSignificance Of The Constraints | How To Solve Any Coding Problem In Your Interview Part 2 ↗Aditya Verma · HindiRead the limit on n first, and it tells you which complexity will pass, before you write a single line of a TLE solution.
08 · Recursion
- ▶ playlistRecursion Playlist | Coding | Interview Questions | Algorithm | Tutorials ↗Aditya Verma · HindiBuilt on one idea: hypothesis, induction, base condition. You learn to trust the smaller call instead of tracing every frame.
- ▶ videoIntroduction to Recursion - Learn In The Best Way ↗Kunal Kushwaha · EnglishA slow, visual first lesson in Java: calls piling up on the stack, the base condition, and the recursion tree.
- ◈ visualizerRecursion Tree and DAG (Dynamic Programming/DP) ↗VisuAlgo (Steven Halim, NUS) · EnglishRun fib(n) and watch the recursion tree explode, then switch to the DAG view to see exactly what memoization saves.
09 · Math & Numbers
- ▶ playlistMaths Playlist | Language Independent Course ↗Striver (take U forward) · EnglishEight short lessons covering GCD, divisors, primes, prime factors, fast power, the sieve and smallest prime factor. That's the number theory interviews actually use.
- ▶ videoModulo Arithmetics | Compute answer modulo 1000000007 | Mathematics Part 3 | DSA-One Course #7 ↗Anuj Bhaiya (Anuj Kumar Sharma) · HindiWhy so many answers are asked 'modulo 10⁹+7', and the modulo rules that keep big answers from overflowing.
- ✎ articleBinary Exponentiation ↗cp-algorithms · EnglishThe reference write-up for computing aⁿ mod m in O(log n). Pow(x, n) and many counting problems use the same idea.
Linear patterns
10 · Arrays & Strings
- ▶ playlistArrays Playlist | Basics to Advanced | C++/Java/Python | DSA | Placements ↗Striver (take U forward) · EnglishClassic array problems (two sum, Kadane, majority element, rotation and more), each solved brute → better → optimal.
- ▶ videoDynamic and Static Arrays ↗William Fiset · EnglishA short, clear look at static vs dynamic arrays and how doubling keeps appends cheap. That's the idea inside ArrayList.
- ▶ video2. Data Structures and Dynamic Arrays ↗MIT OpenCourseWare · EnglishThe MIT 6.006 lecture on why arr[i] is O(1) and how a dynamic array gets amortized O(1) appends. It's the 'why' behind this chapter.
11 · Matrices
- ▶ videoSpiral Traversal of a Matrix | Spiral Matrix ↗Striver (take U forward) · EnglishSpiral order with four shrinking boundaries. The dry run settles the off-by-one corners for good.
- ▶ videoLecture 34: Rotate and Spiral Print a Matrix || DSA Series by Babbar ↗Love Babbar (CodeHelp) · HindiRotate by 90° and spiral print, in Hindi with Java code. These two matrix walks keep coming back in interviews.
- ▶ videoSet Matrix Zeroes | O(1) Space Approach | Brute - Better - Optimal ↗Striver (take U forward) · EnglishGoes from extra arrays to O(1) space by using the first row and column as markers. You'll reuse this in-place trick often.
12 · Two Pointers
- ▶ videoContainer with Most Water - Leetcode 11 - Python ↗NeetCode · EnglishShows with a picture why moving the shorter wall is safe. That argument is the core of every converging two-pointer solution. The code is Python, but the reasoning carries over.
- ▶ video3 Sum | Brute - Better - Optimal with Codes ↗Striver (take U forward) · English3Sum from three loops to a hash set to sort + two pointers, including the duplicate skipping that trips most people.
- ▶ videoL8. Trapping Rainwater | 2 Approaches | Stack and Queue Playlist ↗Striver (take U forward) · EnglishTrapping Rain Water two ways: prefix and suffix maxima, then the two-pointer version that needs no extra arrays.
13 · Sliding Window
- ▶ playlistSliding Window Algorithm | Face to Face Interviews ↗Aditya Verma · HindiTeaches you to recognise a window problem, then gives one format for fixed and variable windows. Bas, the same loop every time.
- ▶ playlistTwo Pointer and Sliding Window Playlist | Language Independent Course ↗Striver (take U forward) · EnglishStarts with the templates, then works through eleven classic problems up to Minimum Window Substring, all built from the same expand-and-shrink loop.
- ▶ playlistSliding Window ↗NeetCode · EnglishShort, visual walkthroughs of the most-asked window problems. Use it as a second explanation when the first one doesn't click.
14 · Hashing
- ▶ videoHashing | Maps | Time Complexity | Collisions | Division Rule of Hashing | Strivers A2Z DSA Course ↗Striver (take U forward) · EnglishHow hashing turns 'how many times did I see this?' into an O(1) lookup, covering frequency arrays, maps, collisions and the division method.
- ▶ videoCount Subarray sum Equals K | Brute - Better -Optimal ↗Striver (take U forward) · EnglishThe prefix sum + HashMap trick, built up slowly from brute force. It's the hardest idea in this chapter.
- ✎ articleIntroduction to Prefix Sums ↗USACO Guide · EnglishRange sums in O(1) after one pass, with Java code and a graded list of practice problems when you want more reps.
15 · Linked Lists
- ▶ playlistLinked List | Beginner to Advanced for FAANG and PBC Interview Rounds ↗Striver (take U forward) · EnglishEvery linked-list topic in order, from making a node to reversal, cycle detection and the hard interview problems.
- ▶ videoLinked List Tutorial - Singly + Doubly + Circular (Theory + Code + Implementation) ↗Kunal Kushwaha · EnglishBuilds singly, doubly and circular lists in Java from scratch. Writing the class yourself is what makes pointer rewiring click.
- ◈ visualizerLinked List (Single, Doubly), Stack, Queue, Deque ↗VisuAlgo (Steven Halim, NUS) · EnglishAnimate insert, remove and search on lists, stacks, queues and deques, and watch the pointers move before you code them.also for 17 · Queues
16 · Stacks
- ▶ playlistStack Playlist | Interview Questions | Coding | Tutorials | Data Structures ↗Aditya Verma · HindiHow to spot a 'nearest greater / smaller' problem, then solving the whole family (up to the histogram) with one monotonic-stack idea.
- ▶ playlistStack and Queue Playlist | Language Independent Series ↗Striver (take U forward) · EnglishStack basics and balanced brackets, then monotonic stacks: next greater element, histogram, stock span and remove K digits.
- ▶ videoDecode String - Leetcode 394 - Python ↗NeetCode · EnglishDecode String with a stack, a clean model for any 'nested brackets' parsing problem. The code is Python, but the stack idea carries over directly.
17 · Queues
- ◈ visualizerLinked List (Single, Doubly), Stack, Queue, Deque ↗VisuAlgo (Steven Halim, NUS) · EnglishAnimate insert, remove and search on lists, stacks, queues and deques, and watch the pointers move before you code them.also for 15 · Linked Lists
- ▶ videoStacks and Queues Complete Tutorial - Theory + Implementation + Types (Dynamic, Circular) ↗Kunal Kushwaha · EnglishBuilds stacks and queues in Java, including dynamic and circular queues, so head and tail wrapping around stops being scary.
- ▶ videoSliding Window Maximum | Sliding Window Algorithm | Deque Data Structure | DSA-One Course #54 ↗Anuj Bhaiya (Anuj Kumar Sharma) · HindiThe monotonic deque behind Sliding Window Maximum, explained in Hindi with Java code. This deque idea comes up a lot in interviews.
18 · Binary Search
- ▶ playlistBinary Search Beginner to Advanced | C++, Java, Python | Notes + Contest ↗Striver (take U forward) · EnglishFrom the basic loop to lower/upper bound, rotated arrays, and binary search on the answer (Koko, aggressive cows, book allocation), in small steps.
- ▶ playlistBinary Search | Interview Questions | Coding | Tutorials | Algorithm ↗Aditya Verma · HindiTrains you to spot binary search where it isn't obvious, on half-sorted arrays and on answer ranges, using one format.
- ✎ articleExtra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken ↗Joshua Bloch · Google Research blog · EnglishThe true story of
(low + high) / 2overflowing inside Java's own Arrays.binarySearch. Read it and you'll writelow + (high - low) / 2for life.
19 · Sorting
- ▶ videoSorting - Part 1 | Selection Sort, Bubble Sort, Insertion Sort | Strivers A2Z DSA Course ↗Striver (take U forward) · EnglishSelection, bubble and insertion sort, each dry-run by hand with its time complexity worked out.
- ▶ videoMerge Sort | Algorithm | Pseudocode | Dry Run | Code | Strivers A2Z DSA Course ↗Striver (take U forward) · EnglishMerge sort with pseudocode, a full dry run and code. Once the merge step clicks, Sort List and inversion counting follow easily.
- ◈ visualizerSorting (Bubble, Selection, Insertion, Merge, Quick, Counting, Radix) ↗VisuAlgo (Steven Halim, NUS) · EnglishWatch every sort in this chapter run on your own input, one comparison at a time, including quicksort and counting sort.
20 · Parsing
- ▶ videoL3. Prefix, Infix, and Postfix Conversion | Stack and Queue Playlist ↗Striver (take U forward) · EnglishConverting expressions between infix, prefix and postfix with a stack. Calculator and expression-parsing problems are built on this.
- ▶ playlistStrings : Popular Interview Problems ↗codestorywithMIK · HindiString problems like String Compression, Count and Say, Reverse Words and Text Justification, each solved intuition-first.
Trees & graphs
21 · Traversals
- ▶ videoBinary Trees Tutorial - Introduction + Traversals + Code | Binary Search Trees (BST) ↗Kunal Kushwaha · EnglishWrites the tree node class in Java from zero and walks through the traversals. Watch this if you want to see the whole thing built by hand.
- ▶ videoL4. Binary Tree Traversals in Binary Tree | BFS | DFS ↗Striver (take U forward) · EnglishA map of every traversal (BFS level order vs DFS pre, in and post order) before you code any of them.
- ▶ videoL37. Morris Traversal | Preorder | Inorder | C++ | Java ↗Striver (take U forward) · EnglishInorder and preorder in O(1) extra space by temporarily threading the tree. It's the follow-up asked after you write the stack version.
22 · Tree Recursion
- ▶ playlistBinary Trees | Binary Search Trees | C++ | Java | Data Structures and Algorithms | Placements ↗Striver (take U forward) · EnglishThe whole tree topic in order, with Java code: traversals, views, LCA, construction from traversals, then BSTs.
- ▶ playlistDynamic Programming on Trees | Interview Questions | Coding | Tutorials | DP on Trees ↗Aditya Verma · HindiOne template: ask the children, return one value up, keep the global best on the side. Applied to diameter and maximum path sum.
- ▶ videoL16. Diameter of Binary Tree | C++ | Java ↗Striver (take U forward) · EnglishDiameter goes from O(n²) to a single O(n) pass that returns height and updates the answer on the way.
23 · BST
- ▶ playlistBinary Tree + BST Full Playlist ↗Anuj Bhaiya (Anuj Kumar Sharma) · HindiShort Java videos in Hindi: implementation, traversals, height, views, diameter and LCA, then BST search, insert, delete and validate. One a day is a good pace.
- ▶ playlistBinary Search Tree Playlist ↗William Fiset · EnglishFive short videos covering what a BST is, insertion, removal in all its cases, traversals and code. That's exactly this chapter's scope.
- ◈ visualizerBinary Search Tree, AVL Tree ↗VisuAlgo (Steven Halim, NUS) · EnglishInsert, search and delete on a live BST. Feed it sorted input to watch it degenerate, then compare with the AVL mode.
24 · Heaps
- ▶ video2.6.3 Heap - Heap Sort - Heapify - Priority Queues ↗Abdul Bari · EnglishThe classic whiteboard lesson on heaps: insert, delete, heapify and heap sort, calm and very clear.
- ▶ playlistHeap Playlist | Interview Questions | Coding | Tutorials | Data Structures ↗Aditya Verma · HindiHow to recognise a heap problem (k-th largest, top k, k closest) and whether a min-heap or a max-heap fits.
- ◈ visualizerBinary Heap (Priority Queue) ↗VisuAlgo (Steven Halim, NUS) · EnglishWatch sift-up and sift-down in both the tree view and the array view, and try the O(n) build-heap yourself.
25 · Tries
- ▶ playlistTrie Series | Striver ↗Striver (take U forward) · EnglishSeven focused lessons: implement a trie, then use it for prefix counts, distinct substrings and maximum XOR.
- ◈ visualizerTrie Visualization ↗David Galles, University of San Francisco · EnglishInsert and find words, and watch shared prefixes get reused. It's a quick way to see why a trie saves work.
- ▶ videoTrie Data Structure | Java DSA Course ↗Apna College · HindiThe trie node class, insert and search built step by step in Java, with notes linked.
26 · Graphs
- ▶ playlistGraph Series by Striver | C++ | Java | Interview Centric | Algorithms | Problems ↗Striver (take U forward) · English56 lessons, from representing a graph in Java to BFS, DFS, cycles, topological sort, shortest paths, DSU and bridges. One series covers the whole topic.
- ▶ playlistGraph Concepts & Qns : Convert Story To Code ↗codestorywithMIK · HindiOpens with 'graph will no more be a nightmare' and means it: representations, BFS, DFS, cycle detection, then DSU and Dijkstra, story first.
- ◈ visualizerGraph Traversal (Depth/Breadth First Search) ↗VisuAlgo (Steven Halim, NUS) · EnglishDraw your own graph and watch BFS and DFS visit it in order. Try it before solving islands or provinces.
27 · Shortest Paths
- ▶ videoG-32. Dijkstra's Algorithm - Using Priority Queue - C++ and Java - Part 1 ↗Striver (take U forward) · EnglishDijkstra with a PriorityQueue, coded in Java. Part 3 (G-34) explains why a plain queue isn't enough and derives the time complexity.
- ▶ videoShortest Path Algorithms (Dijkstra and Bellman-Ford) - Simplified ↗Abdul Bari · EnglishDijkstra and Bellman–Ford side by side on worked examples, in Abdul Bari's calm whiteboard style.
- ◈ visualizerSingle-Source Shortest Paths (Dijkstra/+ve Weighted, BFS/Unweighted, Bellman-Ford, DFS/Tree, Dynamic Programming/DAG) ↗VisuAlgo (Steven Halim, NUS) · EnglishRun BFS, Dijkstra and Bellman–Ford on the same weighted graph and watch every relaxation happen.
28 · Union-Find & MST
- ▶ videoG-46. Disjoint Set | Union by Rank | Union by Size | Path Compression ↗Striver (take U forward) · EnglishUnion by rank, union by size and path compression in one lesson, ending in a small DSU class you can reuse as a template.
- ▶ playlistUnion Find [Disjoint Set] Playlist ↗William Fiset · EnglishFive short videos: the idea, Kruskal's MST with union-find, the union and find operations, path compression, and the code.
- ▶ video3.5 Prims and Kruskals Algorithms - Greedy Method ↗Abdul Bari · EnglishPrim's and Kruskal's on the same graph: two greedy routes to one minimum spanning tree, shown side by side.
29 · Topo Sort
- ▶ videoG-22. Kahn's Algorithm | Topological Sort Algorithm | BFS ↗Striver (take U forward) · EnglishKahn's algorithm with in-degrees and a queue. This BFS version is the one behind Course Schedule.
- ▶ videoTopological Sort Algorithm | Graph Theory ↗William Fiset · EnglishThe DFS version, animated: finish a node, put it in front. Also shows why the order only exists on a DAG.
- ▶ videoCourse Schedule | Apple | Microsoft | Amazon | BFS | Graph Concepts & Qns - 12 | Leetcode 207 ↗codestorywithMIK · HindiCourse Schedule solved with Kahn's algorithm, start to finish. It's the most-asked topological sort problem.
30 · Advanced Graphs
- ▶ videoG-55. Bridges in Graph - Using Tarjan's Algorithm of time in and low time ↗Striver (take U forward) · EnglishBridges with discovery time and low time. The same idea powers articulation points (G-56).
- ▶ videoG-54. Strongly Connected Components - Kosaraju's Algorithm ↗Striver (take U forward) · EnglishStrongly connected components in three steps: order nodes by finish time, reverse the edges, then DFS again.
- ▶ videoTarjan's Strongly Connected Component (SCC) Algorithm (UPDATED) | Graph Theory ↗William Fiset · EnglishTarjan's one-pass SCC algorithm with clear low-link animations. Watch it after Kosaraju for the deeper version.
Paradigms
31 · Backtracking
- ▶ playlistRecursion (Basics to Advanced) and Bactracking Series ↗Striver (take U forward) · EnglishSubsequences, combination sum, subsets, permutations, N-Queens, sudoku and rat in a maze: the full pick / not-pick toolkit in one series.
- ▶ playlistBacktracking ↗Aditya Verma · HindiFirst how to identify a backtracking problem and the general format, then permutations, N-Queens and sudoku using it.
- ▶ videoBacktracking Introduction + Maze Problems - Theory + Code + Tips ↗Kunal Kushwaha · EnglishMaze problems in Java that show exactly why you must undo a step on the way back.
32 · Greedy
- ▶ playlistGreedy Algorithm Playlist | Language Independent Series ↗Striver (take U forward) · EnglishThirteen short greedy problems from easy to hard: jump game, job sequencing, N meetings, interval problems, platforms and candy.
- ▶ video3. Greedy Method - Introduction ↗Abdul Bari · EnglishWhat the greedy method is and when it applies: the theory behind 'make the best-looking move now, never look back'.
- ▤ bookGreedy Algorithms ↗Jeff Erickson, Algorithms (UIUC) · EnglishA free textbook chapter that proves greedy choices correct with exchange arguments. Read it when you want the 'why', not just the 'how'.
33 · Intervals
- ▶ videoMerge Overlapping Intervals | Brute, Optimal with Precise TC analysis ↗Striver (take U forward) · EnglishMerge Intervals from brute force to sort-and-sweep, with a careful time-complexity analysis.
- ▶ playlistLine Sweep Technique: Concepts & Questions ↗codestorywithMIK · HindiLine sweep from scratch, then Meeting Rooms II, Car Pooling and My Calendar. This is the next step after merging intervals.
- ▶ videoL10. Minimum number of platforms required in a railway station ↗Striver (take U forward) · EnglishSort arrivals and departures, sweep, and count the overlap. It's the same problem as Meeting Rooms II, set at a railway station.
34 · Bits
- ▶ playlistBit Manipulation Playlist | Language Independent Course ↗Striver (take U forward) · EnglishOperators, 1's and 2's complement and the must-know tricks, then Single Number I–III, power set and XOR of a range.
- ▶ videoBitwise Operators + Number Systems - Maths for DSA ↗Kunal Kushwaha · EnglishNumber systems and every bitwise operator from scratch, in Java. This is the foundation all the one-line tricks rely on.
- ▶ videoBit Manipulation Algorithms Part 1 | Interview Questions Java C++ | Anuj Bhaiya ✅| DSAOne Course #2 ↗Anuj Bhaiya (Anuj Kumar Sharma) · HindiBinary basics and the common bit tricks in Hindi, with Java code. It's part 1 of a three-video series.
35 · Dynamic Programming
- ▶ videoDP 1. Introduction to Dynamic Programming | Memoization | Tabulation | Space Optimization Techniques ↗Striver (take U forward) · EnglishFibonacci taken from recursion to memoization to tabulation to O(1) space. That's the exact ladder this chapter climbs.
- ▶ playlistDynamic Programming Playlist | Coding | Interview Questions | Tutorials | Algorithm ↗Aditya Verma · HindiFamous for one habit: write the recursion, then memoize, then tabulate. Then whole families (knapsack, LCS, MCM) fall to one parent problem each.also for 36 · DP Patterns
- ▶ video15. Dynamic Programming, Part 1: SRTBOT, Fib, DAGs, Bowling ↗MIT OpenCourseWare · EnglishMIT's SRTBOT recipe for designing any DP: subproblems, relation, topological order, base cases, original problem, time.
36 · DP Patterns
- ▶ playlistDynamic Programming Playlist | Coding | Interview Questions | Tutorials | Algorithm ↗Aditya Verma · HindiFamous for one habit: write the recursion, then memoize, then tabulate. Then whole families (knapsack, LCS, MCM) fall to one parent problem each.also for 35 · Dynamic Programming
- ▶ playlistDynamic Programming Playlist | Interview Questions | Recursion | Tabulation | Striver | C++ | Java | DSA | Placements ↗Striver (take U forward) · English56 lessons grouped by pattern (1D, grids, subsequences, strings, stocks, LIS, partition DP), each taken from recursion to space-optimised.
- ▶ videoTop 5 Dynamic Programming Patterns for Coding Interviews - For Beginners ↗NeetCode · EnglishA short map of the DP patterns behind most interview questions. Watch it first so you know where each new problem fits.
Expert
37 · Design DS
- ▶ videoL18. Implement LRU Cache ↗Striver (take U forward) · EnglishLRU Cache built from a HashMap plus a doubly linked list. It's the design question you will meet most often.
- ▶ playlistDesign Data Structure : Popular Interview Problems ↗codestorywithMIK · HindiMore than 25 design problems (LRU, LFU, Insert Delete GetRandom O(1), Browser History, Design HashMap), thought process first, then code.
- § docsLinkedHashMap (Java SE 17 & JDK 17) ↗Oracle · Java SE 17 API docs · EnglishAccess order plus removeEldestEntry gives you an LRU cache in a few lines. Know it as a follow-up, but expect to build your own.
38 · Range Queries & Strings
- ▶ playlistFenwick Tree/Binary indexed tree playlist ↗William Fiset · EnglishFour short videos covering range queries, point updates, O(n) construction and source code. The lowest-set-bit idea becomes something you can see.
- ▶ videoSegment Trees Tutorial | Range Queries | Interview Questions ↗Kunal Kushwaha · EnglishA segment tree built in Java from scratch: build, query and update, with range-query interview questions.
- ▶ playlistString Matching ↗Aditya Verma · HindiKMP built up from the naive search, then the LPS array, worked examples, code and Longest Happy Prefix.