图的任意两个顶点之间存在循环

Question

查找有向图的两个特定顶点之间的路径数的问题，并且如果它们之间存在循环，则路径数是无限的，因此我知道在整个图中查找循环的算法，但找不到任何两个特定的顶点，所以如果有人解释它对我会有所帮助。

Answer 1

So, we can divide this problem into two sub parts.
If there is a cycle between U (source) and V (destination) then the answer will be infinite. So in one DFS we will start from U until we get V . Similarly starting from V until we get U. If we get reach both from both the ways then the desired answer is infinite.

Now the main part. Run a normal DFS from source U and start visiting every node as true, if you encounter the destination node that is V don't mark it as true and then simply continue from there. (Cycles in between this process can easily be detected).