- Arrays and Strings
- Linked Lists
- Stacks and Queues
- Trees and Graphs
- Bit Manipulation
- Math and Logic Puzzles
- Object-Oriented Design
- Recursion and Dynamic Programming
- System Design and Scalability
- Sorting and Searching
- Testing
- C and C++
- Java
- Databases
- Threads and Locks
- Moderate
- Hard