cppEASYCODING
Warm up with RAII file guard
Easy C++ arena: RAII, resource ownership, move semantics, and exception safety
XP reward
100
Coins
8
Target time
18m
A parser leaks file handles when validation throws halfway through loading. You are working inside a C++ performance arena, and the arena only clears when the result is safe, deterministic, and explainable.
Learning objective
Learn to apply RAII, resource ownership, move semantics, and exception safety in a C++ performance arena while explaining the invariant, safety constraints, and hidden edge cases.
Mission order
A FileGuard wrapper owns a handle and must close exactly once. Implement the direct solution first, then document the one edge case that can break it. Submit the solution plus enough reasoning to pass hidden edge cases.Visible checks
sample case
Expected: 2
empty input
Expected: 0
Clear requirements
- Demonstrates RAII, resource ownership, move semantics, and exception safety
- Handles the visible sample and hidden edge cases
- Keeps output deterministic and explainable
- Avoids unsafe dynamic execution
Secure validation contract
Judge type
CODING
Complexity target
Readable O(n) or O(n log n) baseline
Workspace
Code editor
cppsafe mock judge
Charging editor core
Test Results
Run the visible checks when your first pass is ready.
Clear Protocol
1Read the scenario and restate the expected output shape.
2Run visible checks before chasing hidden edge cases.
3Use Genie for one nudge if stuck, then explain the invariant.
4Submit only when the result is deterministic and safe.
Rewards
XP
100
Coins
8
Mission Route
Hints
Hints are metered and logged for No Hint Hero runs.
Genie Mentor Core
Hint protocol / contextual guardrails active
Progressive hints
Failed-test aware
Solution guarded
Mission: cpp-easy-raii-file-guard0 attempts0 failed tests0 hints used
Progressive hint depth
Genie: Genie online. I use your mission, attempts, failed tests, hints, and path context to coach the next rep without dumping answers first.