Challenge 2: Implement Depth First Search

Problem statement

You have to implement the Depth First Search algorithm on a graph using the data structures, which were implemented in the previous sections.

Note: Your solution should work for both connected and unconnected graphs.

Input

The input is a graph in the form of an adjacency list

Note: You can start the traversal from any vertex.

Output

The output is a string containing the vertices of the graph listed in the correct order of traversal.

Sample input

Graph:

Vertex	Edges
1	3, 2
2	5, 4
3	6
4	None
5	None

Sample output

"124536" or "136254" or "136254" or "136254"