| # Depth-First Search on a Flat Adjacency Matrix | |
| ## Problem Description | |
| Perform depth-first search from the designated source vertex and mark exactly the vertices reachable from it without modifying the input graph. | |
| ## Input | |
| The function receives the graph representation, its size parameters, and the algorithm-specific working or output arrays described by its C signature. | |
| ## Output | |
| The function updates or returns the designated result structure while preserving the read-only graph representation. | |
| ## Constraints | |
| All vertices and edges are within the bounds stated by the function contract, all input graph representations are well formed, and all arithmetic stays within the stated C integer bounds. | |
| ## Source | |
| Classical DFS graph-algorithm problem reconstructed from the verified C artifact. | |