* @brief Helper function to perform DFS and count the number of paths from node `u` to node `v` * @param A adjacency matrix representing the graph (1: edge exists, 0: no edge) * @param u the starting node * @param v the destination node * @param n the number of nodes in the graph * @param visited a vector to keep track of visited nodes in the current DFS path * @retur
source not stored for this graph (policy: none)