问题
I can't think of any algorithm that would find the longest path, that is smaller or equal to some x variable. With Dijkstra's algorithm I can easily get longest path, however I'm not sure if I can use it in my problem.
回答1:
Dijkstra's algorithm will give you the shortest path, not the longest one.
Finding the longest (simple) path is NP-Hard. Since your problem can be degenerated into the longest path problem (take x equal to the sum of all edge weights, which is an upper bound on the length of the longest path), it is also NP-Hard.
You could still use a tree search, but it is not likely to be tractable.
If you are considering non-simple paths (nodes can be traversed several times) then it is a different problem. A degenerate case is the knapsack problem, which is NP-Hard as well.
回答2:
You can use DFS algorithm in order to found longest path. If you search you can found some useful articles, like Depth First Search & Directed Acyclic Graphs.
来源：https://stackoverflow.com/questions/14182476/finding-the-longest-path-that-is-x-weighted-undirected-graph