How to find least-cost paths in a graph using Dijkstra's Algorithm. This video is distributed under the Creative Commons Attribution 2.5 Canada License. creativecommons.org/licenses/b...
thank you! My Uni professor just explained this in such a complicated way.. and you do it within 10 minutes in such an easy way! you are the best, I love you.
This one was very helpful. The other video I watched gave me the impression we chose the new vertex from the list of unvisited adjacent vertices because the graphs were too simple. This one was complex enough (having h have only one path leading in) that it made it clear we are choosing the next vertex to check just from the list of unvisited vertices. Thank you.
This is the best explanation for Dijkstra's that I have seen on the net. I was having a hard time with this algorithm until I saw it explained like this. It helped me finish my project. Perfect!
Yes! Finally someone made a Witcher reference. I was browsing xkcd and suddenly "Dijkstra's algorithm" came out of nowhere. I was like "What sorcery is this??"
Thank you very very much. You explained it well and I understood it well. My teacher didn't haven't taught us this (as far as I remember), but gave us an assignment which we have to use this method to solve (it said so in the problem, as in we have to specifically use this method). So I'm really really thankfull for this video. Once again, thank you.
OMG that was amazing i was desperate to understand this thing cause there are only 4 hours till my final and then i found this tutorial when i was revising thnq so much you saved me
Thanks a Lot !! I have Exam tomorrow too !! This algorithm has been a headache to me for a long time untill I saw and understood your very good leçon a few seconds ago ! Thanks again Sir !
I love your explanation about algorithm. what is your youtube channel ?. your explanation on BFS and DFS destroyed my 15 year old fear about Graph problems. you explain things 1000 better than a Professor of MIT. Thank you !!!
Now to find other paths, for example, as you said, D to H or H to G, you use the same method that the instructor used in this video. Notice that the instructor started with A - this was his starting vertex. To find a path from a vertex other than A, simply use the same method starting with that vertex instead (for your problems, D or H respectively) Hope all of this helped! :)
wow, now if math teachers could find ways to be this straightforward and concise in their teaching, we'd all be astrophysicists by now. Nice explanation
This is an outstanding video. The only example or scenario that seems to be missing is how to manage/make a decision when you have two (2) edges from the same node (so two different path options from the same node) that cost the same...e.g. going from F to C or from F to D and they both cost 40.
Note I'm just a student practising this, so I'm not sure if it's correct but seems to have worked and made sense, at least for me so far. But still take it with a massive grain of salt, and if somebody could correct me that'd be great choose either one, just make sure it's the shortest one or among the shortest routes as calculating using shortest routes is the whole point of the algorithm. Also if to a certain node you have got 2 paths of the same length, just write something like 60, (A, D) down into the table. For example, if both A and D lead to E at a cost of 60 each, write 60, (A, D) under E. Then you can pick either one, the point is just to cover all the nodes.
B:20, C:40, D:50, E:N/A, F:30, G:70, H:60. For clarity, ignore the "small letters" under the numeric line values; they represet the "via node". Each line value from left to right aligns with each Goal Node's "main column", starting with B (focus on the letters written in blue at the top). That stated, to get the shortest path from A to Goal n: read *only* the numerical values on the final line (#7). (first value is for B .. last value is for H).
All examples i found on YT start from the vertex a (the very first vertex) and go to the z(the last one that is located last on the right). What if the starting point is a middle vertex? Shall we go through all the paths even those who are left even our end is on the right?
to get a best path, take for e.g. the best path from A to D (obtained with Dijkstra's alg), you follow the reverse path given by the parents from which they were explored. So starting from D, you see that it was visited from parent C and has a cost of 50. Now going to C, you see that its parent is F. And F was visited through B (its parent). And finally, B's parent is A. So the path would be A-B-F-C-D. The idea is that you have to reconstruct your path from _goal_ node to the _starting_ node.
