Computer Science Fundamentals Roadmap

How to read nested loops and recursive calls, amortized analysis of dynamic array append, and worked Big-O walkthroughs.

How hashing, buckets, and collisions work, average vs worst-case complexity, and solving two sum with a hash map.

Tree terminology, BST insert/search/delete, the four traversal methods, and when a BST degrades to O(n).

Track connected groups in near-constant time with union by rank and path compression — and solve classic graph problems with it.

Bubble sort, merge sort, and quicksort with full code, a complexity/stability comparison table, and when to just use sorted().

The backtracking template — choose, explore, un-choose — applied to subsets, permutations and N-Queens, with pruning.

What makes a choice greedy, a coin-change counterexample where greedy fails, and activity selection solved correctly with greedy.

Overlapping subproblems and optimal substructure, top-down vs bottom-up on climbing stairs, and 0/1 knapsack solved with a table walkthrough.

Dijkstra's algorithm for weighted shortest paths, when to reach for Bellman-Ford instead, and a complete Union-Find implementation.

What an operating system does, kernel vs user mode, system calls, and the difference between processes and threads.

Race conditions, mutexes, semaphores, the producer–consumer problem, and the four conditions for deadlock — with Python demos.

Stack vs heap, paging, page tables, virtual memory, page faults and page replacement algorithms like LRU and FIFO.

How data travels across networks, the OSI and TCP/IP layer models, packets, encapsulation and the role of each layer.

Why schema design matters and the process: identifying entities, relationships, and constraints.

Single responsibility, open/closed, Liskov substitution, interface segregation and dependency inversion — with before/after code.

How distributed nodes agree despite failures — Raft leader election and log replication, Paxos in brief, and where this shows up in etcd and ZooKeeper.

Commonly asked algorithms interview questions with clear, practical answers.