# Depth-First Search on a Two-Dimensional 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.