Problem-Solving Case Studies

108 case studies for the course's signature teaching activity: the case method for programming. The instructor projects one case, students think for ~5 minutes, the class discusses approaches, and only then is the worked solution revealed.

108 cases · 5 difficulty tiers · every case tied to a lecture (L01–L32) · projector files contain NO solutions.

Worked solutions, discussion points, and grading notes live in the instructor-only area — see instructor/case_studies/README.md (restricted content; students should not open it).

How a case runs in class (≈15 minutes)

Phase	Time	What happens
Project	0:00	Instructor shows the case from the projector file
Think	5 min	Students work on paper — no keyboards, no compiler
Discuss	5–7 min	Students propose approaches; instructor routes, does not correct
Reveal	2–3 min	Worked solution + discussion points from the instructor file
Extend	homework	The extension challenge becomes an optional task

The paper-only rule is the point: it forces planning before typing — the single most valuable habit this activity trains.

Case anatomy

Every projector case contains exactly these fields:

Case ID (PF-CS-NNN) and title
Difficulty tier (1–5, see below)
Related lecture / module (L07 · Module 4)
Context — a real-world or computational scenario
Problem statement — unambiguous, no hidden requirements
Input / Output — exact formats
Constraints — explicit ranges so edge cases are fair game
Thinking questions — 3–4 prompts that scaffold the discussion
Hints (progressive) — three escalating nudges, shown on request

The instructor's parallel file adds: expected concepts, common incorrect approaches, instructor discussion points, solution outline, worked C++ solution, test cases, and the extension challenge. The extension challenge is public (it appears on the projector after the reveal); worked extensions stay in the instructor area.

Tiers

Tier	Name	Cases	Lectures	Character
1	Beginner	CS-001–020	L01–L12	Trace, predict, read I/O, first decisions/loops
2	Foundational	CS-021–040	L13–L16	Number algorithms, function design, decomposition
3	Intermediate	CS-041–060	L17–L24	Arrays, strings, searching, sorting, counting
4	Advanced	CS-061–080	L23–L30	Complexity, pointers, dynamic memory, records
5	Expert introductory	CS-081–108	L29–L32	Files, validation pipelines, classes, synthesis

Tiers are difficulty bands, not a strict lecture gate — Tier 2 cases may appear in week 9 for revision. Within each file, cases ascend in difficulty.

Files

case-studies/
├── README.md            ← this file
├── by_tier/             ← PROJECTOR files (questions + hints only)
│   ├── tier1_beginner.md
│   ├── tier2_foundational.md
│   ├── tier3_intermediate.md
│   ├── tier4_advanced.md
│   └── tier5_expert_introductory.md
└── index.md             ← ID → lecture → tier → concept map

Instructor copy	Content
`instructor/case_studies/solutions_tier1.md` … `solutions_tier5.md`	Solution outline, worked code, test cases, discussion points, misconceptions
`instructor/case_studies/README.md`	How to run the activity, pacing, rubric

Policies

No solutions in projector files. Hints stop at nudge level; nothing that reveals an algorithm.
Compilation status: worked solutions in the instructor area were compiled and executed with the case's test cases (see ../docs/CASE_STUDY_AUDIT.md for evidence). Projector files contain no code to compile.
Standards: C++17 per ../docs/CPP_STANDARD.md; code style per ../docs/CODE_STYLE.md.
Case IDs are permanent: retired cases are marked retired, never renumbered.

The five tiers

The data-science section supplements the main bank: DS case studies (PF-DS-CS-1…8).