DFS Checker Codeforces

This tool targets competitive programmers solving Codeforces problems that rely on DFS traversal behavior. It accepts a graph description, problem context, and an optional submission or traversal policy to validate expected behavior. By focusing on traversal order, edge handling, and component coverage, it helps identify subtle DFS logic errors prior to submission. Conceptually, the checker builds a graph model from provided nodes and edges, respects directed vs undirected edges, and performs a reference DFS following a defined neighbor order. It then simulates the candidate's traversal, compares the produced sequence and visited set against the reference, and flags deviations such as premature visits, skipped nodes, or incorrect handling of cycles and back edges. It supports 1-based CF indexing and can operate with or without actual code execution depending on the input scenario. Beneficiaries include CF contestants validating their solutions, coaches teaching DFS properties, and platform maintainers seeking reproducible problem checks. Differentiators include flexible graph representations, deterministic traversal order, detailed mismatch reporting, and robust handling of edge cases like isolated nodes, multi-edges, and self-loops without requiring full judge integration. Core features include input validation, graph normalization, DFS simulation, result comparison, and exportable mismatch summaries. Typical use cases cover practice problems, editorial verifications, and classroom demonstrations. Use cases illustrate how discrepancies in visit order or neighbor selection influence outputs, aiding faster debugging and deeper understanding of DFS behavior.