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bff4ec7 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | # Depth-First Search on an Adjacency List
## Problem Description
Given a directed graph whose vertices are numbered from `0` to `vertex_count - 1`, perform a depth-first search starting from a valid source vertex. The graph is stored as an array of linked lists: `adjacency[u]` contains exactly the outgoing neighbors of vertex `u`.
The graph representation is read-only. The procedure updates the caller-provided `visited` array so that, when it returns, a vertex is marked if and only if it is reachable from the source vertex.
## Input
- `adjacency`: an array of linked-list heads representing all outgoing adjacency lists.
- `vertex_count`: the number of vertices.
- `visited`: an integer array of length `vertex_count`, initially marking no vertex as visited.
- `vertex`: the source vertex from which the traversal starts.
## Output
The function returns no value. It updates `visited` in place so that exactly the vertices reachable from `vertex` are marked as visited. The graph stored in `adjacency` is unchanged.
## Constraints
- `0 < vertex_count < INT_MAX`.
- `0 <= vertex < vertex_count`.
- Every neighbor appearing in an adjacency list is a valid vertex.
- The graph representation is well formed.
- The initial visited set is empty.
## Source
Classical depth-first search problem reconstructed from the verified C artifact.
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