Section 4 of 9

DSA Curriculum: Beginner → Advanced

Data structures & algorithms path with famous problems and verified free YouTube resources.

Progression assumes you can already code (you can — TypeScript/JavaScript counts; most resources below use Python/Java/C++ but NeetCode has JS/TS solutions). Recommended pace: Beginner 4–6 weeks, Intermediate 8–10 weeks, Advanced 6–8 weeks at ~1.5 hrs/day.

BEGINNER

Topic	One-line explanation	Practice problems (platform)	Free YouTube resources
Big-O / Complexity Analysis	Measuring how runtime/memory scales with input size.	”Two Sum” (LeetCode 1) — compare O(n²) vs O(n) solutions; “Contains Duplicate” (LeetCode 217)	NeetCode — “Big O Notation - Full Course” segments inside playlists; Abdul Bari — “1.5 Time Complexity” (Algorithms playlist)
Arrays & Strings	Contiguous data; the substrate of most interview problems.	”Best Time to Buy and Sell Stock” (LeetCode 121); “Product of Array Except Self” (LeetCode 238); “Valid Anagram” (LeetCode 242)	NeetCode — “Arrays & Hashing” section of NeetCode 150 playlist; Striver (takeUforward) — A2Z DSA Course, Arrays playlist
Hash Maps / Sets	O(1) average lookup by key; trade memory for speed.	”Group Anagrams” (LeetCode 49); “Longest Consecutive Sequence” (LeetCode 128)	NeetCode — “Group Anagrams” and hashing videos in NeetCode 150; freeCodeCamp — “Data Structures Easy to Advanced Course” (William Fiset, hash table section)
Two Pointers	Two indices moving through data to avoid nested loops.	”Valid Palindrome” (LeetCode 125); “Container With Most Water” (LeetCode 11); “3Sum” (LeetCode 15)	NeetCode — Two Pointers section, NeetCode 150; Striver — Two Pointer playlist (takeUforward)
Sliding Window	Maintain a moving subrange; turns O(n²) substring problems into O(n).	”Longest Substring Without Repeating Characters” (LeetCode 3); “Minimum Window Substring” (LeetCode 76)	NeetCode — “Sliding Window: Best Time to Buy/Sell Stock” and window section of NeetCode 150
Stacks & Queues	LIFO/FIFO structures; parsing, undo, BFS foundations.	”Valid Parentheses” (LeetCode 20); “Min Stack” (LeetCode 155); “Daily Temperatures” (LeetCode 739)	NeetCode — Stack section, NeetCode 150; Abdul Bari — stack/queue lectures in Algorithms playlist
Binary Search	Halve the search space each step on sorted/monotonic data.	”Binary Search” (LeetCode 704); “Search in Rotated Sorted Array” (LeetCode 33); “Koko Eating Bananas” (LeetCode 875)	NeetCode — Binary Search section; Striver — “Binary Search Playlist
Linked Lists	Nodes chained by pointers; insertion cheap, random access expensive.	”Reverse Linked List” (LeetCode 206); “Merge Two Sorted Lists” (LeetCode 21); “Linked List Cycle” (LeetCode 141)	NeetCode — Linked List section; freeCodeCamp — William Fiset data structures course (linked list section)
Recursion basics	Function calling itself on smaller subproblems; base case + recursive case.	”Climbing Stairs” (LeetCode 70) recursively; “Pow(x, n)” (LeetCode 50)	Abdul Bari — “How to write Recursive Functions” + recursion series (Algorithms playlist); Striver — Recursion playlist

INTERMEDIATE

Topic	One-line explanation	Practice problems (platform)	Free YouTube resources
Trees & BSTs	Hierarchical nodes; BST keeps sorted order for O(log n) ops.	”Invert Binary Tree” (LeetCode 226); “Validate Binary Search Tree” (LeetCode 98); “Binary Tree Level Order Traversal” (LeetCode 102)	NeetCode — Trees section, NeetCode 150; Striver — Binary Trees playlist (takeUforward)
Heaps / Priority Queues	Always pop the min/max in O(log n); top-K and scheduling problems.	”Kth Largest Element in an Array” (LeetCode 215); “Merge k Sorted Lists” (LeetCode 23); “Find Median from Data Stream” (LeetCode 295)	NeetCode — Heap/Priority Queue section; William Fiset — “Priority Queue” videos (data structures playlist)
Backtracking	Try a choice, recurse, undo — exhaustive search with pruning.	”Subsets” (LeetCode 78); “Combination Sum” (LeetCode 39); “N-Queens” (LeetCode 51)	NeetCode — Backtracking section; Striver — Recursion & Backtracking playlist
Graphs: BFS/DFS	Networks of nodes/edges; BFS = shortest unweighted path, DFS = reachability/structure.	”Number of Islands” (LeetCode 200); “Clone Graph” (LeetCode 133); “Rotting Oranges” (LeetCode 994)	William Fiset — “Graph Theory Algorithms” playlist / freeCodeCamp “Graph Algorithms for Technical Interviews”; Striver — Graph Series (takeUforward)
Topological Sort	Order tasks so every dependency comes first (DAGs only).	”Course Schedule” (LeetCode 207); “Course Schedule II” (LeetCode 210); “Alien Dictionary” (LeetCode 269, premium)	William Fiset — “Topological Sort” (Graph Theory playlist); NeetCode — “Course Schedule” video
Tries	Prefix tree — char-by-char storage for autocomplete/dictionary problems.	”Implement Trie” (LeetCode 208); “Word Search II” (LeetCode 212)	NeetCode — Tries section, NeetCode 150
Intervals	Sort by start, then merge/scan — meetings, ranges, bookings.	”Merge Intervals” (LeetCode 56); “Insert Interval” (LeetCode 57); “Non-overlapping Intervals” (LeetCode 435)	NeetCode — Intervals section, NeetCode 150
Greedy	Take the locally best choice; works when local optimum ⇒ global optimum.	”Jump Game” (LeetCode 55); “Gas Station” (LeetCode 134); “Task Scheduler” (LeetCode 621)	NeetCode — Greedy section; Abdul Bari — Greedy method lectures (Algorithms playlist)
1-D Dynamic Programming	Cache overlapping subproblem answers; recursion + memo table.	”House Robber” (LeetCode 198); “Coin Change” (LeetCode 322); “Longest Increasing Subsequence” (LeetCode 300)	NeetCode — 1-D DP section; Striver — DP Series (“Dynamic Programming Playlist,” takeUforward); freeCodeCamp — “Dynamic Programming - Learn to Solve Algorithmic Problems”

ADVANCED

Topic	One-line explanation	Practice problems (platform)	Free YouTube resources
2-D / Multidim DP	DP over grids or two sequences (edit distance, LCS family).	”Longest Common Subsequence” (LeetCode 1143); “Edit Distance” (LeetCode 72); “Burst Balloons” (LeetCode 312)	NeetCode — 2-D DP section; Striver — DP on Strings/Grids (DP Series)
Shortest Paths (Dijkstra, Bellman-Ford)	Weighted-graph shortest paths; Dijkstra = no negative edges, Bellman-Ford handles them.	”Network Delay Time” (LeetCode 743); “Cheapest Flights Within K Stops” (LeetCode 787); “Path With Minimum Effort” (LeetCode 1631)	William Fiset — “Dijkstra’s Shortest Path Algorithm” (Graph Theory playlist); Abdul Bari — “Bellman-Ford” lecture
Union-Find (DSU)	Near-O(1) merge/find of disjoint sets; connectivity & cycle detection.	”Redundant Connection” (LeetCode 684); “Accounts Merge” (LeetCode 721); “Number of Provinces” (LeetCode 547)	William Fiset — “Union Find” videos (data structures playlist); NeetCode — “Redundant Connection”
Minimum Spanning Tree (Kruskal/Prim)	Cheapest edge set connecting all nodes.	”Min Cost to Connect All Points” (LeetCode 1584)	William Fiset — Kruskal/Prim videos (Graph Theory playlist); Abdul Bari — MST lectures
Bit Manipulation	Operate on numbers at the bit level; XOR tricks, masks.	”Single Number” (LeetCode 136); “Counting Bits” (LeetCode 338); “Sum of Two Integers” (LeetCode 371)	NeetCode — Bit Manipulation section, NeetCode 150
Monotonic Stack / Advanced Stack	Stack kept sorted to answer “next greater/smaller” in O(n).	”Largest Rectangle in Histogram” (LeetCode 84); “Trapping Rain Water” (LeetCode 42)	NeetCode — “Largest Rectangle in Histogram”, “Trapping Rain Water” videos
Segment Trees / Fenwick (BIT)	Range queries + point updates in O(log n); competitive-programming staple.	”Range Sum Query - Mutable” (LeetCode 307); “Count of Smaller Numbers After Self” (LeetCode 315)	William Fiset — Fenwick tree videos (data structures playlist); Striver — Segment Tree playlist [UNVERIFIED — check current playlist name]
String Algorithms (KMP, Rabin-Karp)	Linear-time pattern matching via prefix functions or rolling hashes.	”Find the Index of the First Occurrence in a String” (LeetCode 28); “Shortest Palindrome” (LeetCode 214)	Abdul Bari — “KMP String Matching Algorithm”; Striver — String playlist
Advanced Graph (SCC, bridges)	Tarjan/Kosaraju find strongly connected components and critical edges.	”Critical Connections in a Network” (LeetCode 1192)	William Fiset — “Tarjan’s Strongly Connected Components”, “Bridges and Articulation points” (Graph Theory playlist)

Strategy notes

Follow one structured list, not random problems: NeetCode 150 (free at neetcode.io) or Striver’s A2Z DSA Sheet (free at takeuforward.org). Both map 1:1 to their YouTube playlists.
For an Angular/TS dev: solve in TypeScript/JavaScript on LeetCode — allowed in nearly all interviews; switching to Python for AI work can come later (Task 5).
Target: ~150–200 curated problems total beats 500 random ones. Redo failed problems after 1 week (spaced repetition).

Think of DSA (Data Structures and Algorithms) as learning to organize and search a warehouse efficiently. A data structure is a way of arranging boxes (data) — on shelves, in stacks, in a sorted catalog. An algorithm is a step-by-step recipe for finding or rearranging those boxes fast.

Why it matters: tech interviews at most companies are essentially warehouse-efficiency puzzles. Even with AI writing code, companies test this because it shows you can reason about cost — will this approach take 1 second or 3 hours when the data gets huge?

The three levels, in warehouse terms:

Beginner — Learn the basic storage types: a row of shelves (arrays), a labeled filing cabinet where you jump straight to the right folder (hash maps), a stack of trays where you only take the top one (stacks), and the trick of guessing a word in the dictionary by always opening to the middle (binary search).
Intermediate — Learn branching structures: family trees (trees), city road maps (graphs — how apps like Google Maps think), “to-do lists with dependencies” (topological sort — you must wear socks before shoes), and the powerful trick of writing down answers to sub-puzzles so you never solve the same one twice (dynamic programming).
Advanced — Specialist tools: finding the cheapest road network connecting cities (minimum spanning trees), instantly answering “what’s the total between shelf 40 and shelf 90” even while boxes keep changing (segment trees), and finding a phrase inside a giant book in one pass (string matching).

How to learn free: two teachers dominate YouTube — NeetCode (clear 15-minute explanations of famous interview puzzles, US-style) and Striver / takeUforward (a complete free A-to-Z course, very popular in India). Practice happens on LeetCode, a free website with thousands of these puzzles where your solution is auto-checked.

Realistic timeline: about 4–6 months at 1–1.5 hours a day to go from beginner to interview-ready. It’s a gym membership, not a weekend project — consistency beats intensity.

Diagrams

Interview question topic frequency (directional estimate)

Directional estimate — exact split varies by company. Not independently verified in this research pass. · [UNVERIFIED] directional industry consensus

Data table

Category	Value
Arrays / Strings	38%
Trees / Graphs	28%
Dynamic Programming	18%
Design / Other	16%

Sources

All resources confirmed to exist via live web search, July 2026.

NeetCode 150 list + video map ✅ verified
NeetCode YouTube channel ✅ verified
Striver’s A2Z DSA Course/Sheet ✅ verified
Striver’s A2Z DSA Course YouTube playlist ✅ verified
Abdul Bari — Algorithms playlist (84 videos) ✅ verified
William Fiset — Graph Theory playlist ✅ verified
freeCodeCamp — Data Structures Easy to Advanced Course (William Fiset, 8 hr) ✅ verified
freeCodeCamp NeetCode 150 course (38 hr) ✅ verified
LeetCode problem set ✅ verified

✅ = existence verified via live search, July 2026. Individual video titles inside playlists may shift; playlist/channel links are the stable anchors.