Add depth first search for graphs

[czgdp1807]

Description of the problem

Serial and Parallel version of depth first search are required to be added for graphs.

Example of the problem

References/Other comments

.. [1] https://en.wikipedia.org/wiki/Depth-first_search
.. [2] https://research.nvidia.com/sites/default/files/publications/nvr-2017-001.pdf

It looks like its too costly to implement parallel DFS as the algorithm is inherently sequential.

[asaw4]

i would like to work on this problem. please assign me this problem

[czgdp1807]

Are you participating through GSSoC, 2020?

[kritika12298]

I would like to work on this problem, please assign me

[czgdp1807]

Hi, @kritika12298
Feel free to start with the serial version of DFS. Please propose an API for the same(the function name, arguments for the function). I have proposed an API for BFS at #82 (comment) and #82 (comment)
Something similar can be done for DFS as well.
P.S. We don't assign issues to contributors, however, this doesn't mean that they are not allowed to work on that issue. We think a PR is more important than assigning issues, so whenever you do make a PR, the issue will be linked to that PR and you can keep working on it.
Let us know in case you face problems/queries.

[kritika12298]

Okay thank you

[soumyarao17]

Hello Sir! I would like to contribute to this project. As far as I have understood, proposing an API means writing the name of the function and its arguments. So, here I have made this function for the same:

1. addEdge(self,v,visited) //for adding the edge
2. DFShelper(self, v, visited) // a helping function for the DFS function
3. DFS(self,v) // function for DFS traversal

These are the main functions. I have also written the entire code for this. If you want, I can share it as well.
If something is misunderstood by me or needs any changes, please inform me.

[czgdp1807]

@wowrao17 The API for depth first search should be along the lines of breadth first search. See, https://github.com/codezonediitj/pydatastructs/blob/master/pydatastructs/graphs/algorithms.py
DFS cannot be made parallel due to its inherently sequential nature. There are some publications which claim to have made it parallel but it's too costly to implement their ideas.

[imgolash]

I would like to work on it.

[czgdp1807]

@golashboy You can work on it. Please go through https://github.com/codezonediitj/pydatastructs/wiki/Plan-of-Action-for-the-Projects to see the steps for adding any data structure or algorithm. The API for depth first search should be similar to

pydatastructs/pydatastructs/graphs/algorithms.py

Lines 22 to 23 in 797ec26

	def breadth_first_search(
	graph, source_node, operation, *args, **kwargs):

[imgolash]

Ok thanks