Biologists often construct a food network of species in an ecosystem. the vertices represent species, and a directed edge (u, v) means species u eats species v. an apex species is one that is not eate

Biologists often construct a food network of species in an ecosystem. the vertices represent species, and a directed edge (u, v) means species u eats species v. an apex species is one that is not eaten by another species. suppose you are give a list of all possible "eating" relationships (so a list of "u eats v"). determine all apex species.