Recognizing hidden bicircular networks

In this and a subsequent paper, the authors introduce a polynomial-time algorithm for transforming an m×n matrix A by projective equivalence into the generalized incidence matrix of a bicircular generalized network N when such a matrix exists. In this paper, they construct the underlying graph G of N by an algorithm of worst-case complexity m²n². In the sequel, the authors assign arc weights to G to obtain N and the projective equivalence.