Longest Path in Directed Acyclic Graph (DAG)

Given a Directed Acyclic Graph (DAG) with a specific number of edges and vertices, your task is to determine the longest path reachable from a given source vertex.

Input:

The first line describes an integer 'T', representing the number of test cases.

Each test case begins with a pair of integers 'V' and 'E', representing the number of vertices and edges.

The next 'E' lines contain two space-separated integers 'X' and 'Y', describing a directed edge from vertex 'X' to vertex 'Y'.

The last line in each test case provides a single integer 'S' representing the source vertex.

Output:

For each test case, output the distance to the farthest vertex reachable from vertex 'S'.

Example:

A DAG might look like:

Source node: 1 The farthest vertex in the given graph from vertex 1 is 2, via the path through vertex 3. Hence, the distance is 2.

Constraints:

• 1 <= T <= 10
• 1 <= V <= 10^3
• 1 <= E <= 3*10^3
• 1 <= X, Y <= V - 1
• 0 <= S <= V - 1

Note: Implement the function only; input/output has been handled.