I have a directed graph for which I am trying to find the top k shortest paths. At the moment I have implemented the network in graph-tool which provides a shortest path algorithm but no k shortest paths algorithm by what I can tell. I have come across this post (All shortest paths using graph_tool) but I am not after all paths connecting two nodes.
It seems as if NetworkX has a function implemented for this (https://networkx.readthedocs.org/en/stable/reference/generated/networkx.algorithms.shortest_paths.generic.all_shortest_paths.html?highlight=all_shortest_paths). Is there a way to somehow do this in graph-tool too or am I better off switching toolboxes and using NetworkX?
This is available in the git version: https://graph-tool.skewed.de/static/doc/dev/topology.html#graph_tool.topology.all_shortest_paths
Related
I need to set up the argument "-shortest" but in c++ code. I know that I can set up an argument with value for example:
av_opt_set(codecContext, "crf", "28", 0);
But here is the thing, there is a value, but in shortest no value.
So how can I set up shortest in c++ code
Thanks in advance
I got an answer here: https://www.reddit.com/r/ffmpeg/comments/oeuwlw/how_to_set_up_shortest_flag_programmatically_c/
So,
-shortest is a part of ffmpeg binary. Not available when working with the libav* libs.
You can set "fflags", "shortest" and "max_interleave_delta", "100M" on the AVFormatContext.
I am currently trying out Task #2 in the 2016/2017 COCI. Although I have attempted to solve this problem, I couldn't do it.
So, I looked at the solution and it said,
In order to solve this task, we need to find any path Barry can take
from the initial position to any position in the last column. We can
do this by using BFS or DFS algorithm, after which we need to
construct the path. Finally, all that’s left is to format the path
according to the task.
So I went ahead and studied the BFS and DFS algorithm. However, I am not sure how I can implement this algorithm into my program.
Although I can find certain elements in a tree with the algorithm, I don't know how to use it to find a pathway.
So can someone tell my, briefly, how to use the BFS/DFS algorithm to solve the programming problem?
Thanks in advance.
This is the contest page:
http://hsin.hr/coci/archive/2016_2017/contest1_tasks.pdf
What you could do is convert the whole map into a tree.
Here is a diagram I made to demonstrate what I exactly mean:Click here to view the image
Hope that made sense.
I want to be able to use bfs in BGL to find all the trees of a forest, which is basically finding connected components using multiple source vertices. For example, it may be used to find different connected regions of an image to enable image segmentation (this is just one of the cases). How can I use the breadth_first_search in BGL to do this? Any pointers to examples/sources would be greatly appreciated! I have surveyed BGL documentation and have not been successful in finding what I want to do.
Just use the connected components that already exists in boost. There is a useful example. Afterwards all vertices in the graph will have a mapping to their component. If you really want to use BFS on individual parts, just use a visitor and push nodes into a vector.
You can specify your start node with:
breadth_first_search(graph, visitor(vis).root_vertex(root_vertex_descriptor));
I'm having trouble figuring out how exactly to get this to work... I'm attempting to get the shortest path to the goal using a DFS. I know that BFS is better but I was asked to use DFS for this. As you can see, I attempt to make a comparison between all stacks that lead to the end to find the goal, but it does not work, only the first stack that leads to the goal is ever printed... I know somewhere I need to unvisit nodes, but I cannot figure out exactly how. Right now I do get a path to the goal, but not the shortest one. Any help with this would be greatly appreciated.
Writing a non-recursive DFS is possible by using your own stack, but I find the recursive solution to be more elegant. Here is a sketch of one:
DFS(vertex)
path.push_back(vertex)
visited[vertex] = true
if we found the exit
output path
else
for each neighbor v of vertex
if not visited[v]
DFS(v)
visited[vertex] = false
path.pop_back()
I am new to graph theory and graph concept.
I am workign on something, that requires me to create a mesh(Undirected graphs) with n number of nodes.
Once the structure is created, I would be running various algorithms on the structure, to find a shortest path from a node to other.
No for this I have decided to use Boost graph librabry.
I read through the online documentation. The online documentation is good but at the same time not sufficient.
I went through various examples online and everywhere, they import the graph from Graphviz.
If i am not wrong, we have to manually draw or write a dot program to get a graph in Graphviz and import in .dot format(Please correct me if i am wrong)
But is there a way in Boost where I could create a graph, instead of importing it from GraphViz?
And I would let user to decide the number of vertices in it, instead of pre-defining it.
Any help would be very much appreciated.
Thanks a ton in advance.
It's maybe not very correct, but I am giving a response a gave before.
https://stackoverflow.com/a/3100220/202083
You can see how to programmaticaly add nodes and edges.
I hope this is enough for you to get started.