singly connected problem

A directed graph G = (V, E) is singly connected if u ->v implies that G contains at most one simple path from u to v for all vertices u, v V . Give an efficient algorithm to determine whether or not a directed graph is singly connected. Problem definition: A directed graph G is singly connected if there is at most one simple (i.e. no repeated vertex) path from u to v for every vertex in G. Given an algorithm to determine whether or not a directed graph is singly connected. Input: First line is N, denotes the amount of test case, then there are Ns graph data followed by N. Second line is V, each graph data is composed of V (the number of vertices, 4, the first vertex number is 0 of all the vertex). Each vertex is an integer in [0, n-1], also notes that the input edge is not ordered by the start vertex. Output: If the input graph is singly connected, output the YES, or NO if not. The test case number should be printed before the answer.

Example of Input:

1 6 8 0 1 0 4 1 2 2 0 2 1 3 2 4 5 5 4 Output: 1 NO

please using c++ programming language and follow my INPUT and OUTPUT formats ,thank you .