20 C# Programming Challenges (A Level)

20 C# challenges for A Level Computer Science: stacks, queues, linked lists, trees, hash tables, graphs, Dijkstra, OOP. Compiled, tested solutions. H446.

Almost everything on Tes for A Level programming is Python. This pack is for departments that teach C# — OCR H446 centres and AQA 7517 centres taking the C# option — and makes students build the things the exam asks them to describe. Every challenge has a model solution that has been compiled and run against the example input, a mark scheme and teaching notes.

Silver (1–10, 8 marks each): temperature statistics with arrays, a number classifier, a Caesar cipher with char arithmetic, word frequency with Dictionary, a recursion toolkit with a printed call trace, an array-based stack used for bracket matching, a circular queue print simulation, bubble vs insertion sort with comparison counts, binary search iteratively and recursively, and student records sorted and tabulated. Gold (11–20, 10 marks each): an encapsulated BankAccount with exceptions and a static counter, an abstract Shape hierarchy, a linked list from scratch, a BST with in/pre/post-order traversal, recursive merge sort and quick sort, a hash table with chaining and a collision count, BFS and DFS with shortest-path reconstruction, Dijkstra’s algorithm on an adjacency matrix, a defensive CSV loader with a custom exception and an interface, and a capstone library system with file persistence.

You get: student booklet (23-page PDF + editable Word, no answers); teacher pack (48-page PDF + editable Word) with mark schemes, full model solutions, teaching notes and a specification map (OCR H446 1.2.4, 1.4.2, 2.1.3, 2.2, 2.3.1; AQA 7517 4.1–4.3); all 20 solutions as .cs console programs plus the two data files. Solutions use only what students need for the exam — classes, properties, inheritance, abstract classes, interfaces, generic collections, exceptions, System.IO — and no LINQ, so the algorithms stay visible. Python and Java students can attempt every challenge. More at learncomputing.org.