Recognizing Outerplanar Graphs in Linear Time

This paper describes a linear time algorithm to determine whether an arbitrary graph is outerplanar. The algorithm uses an edge coloring technique and deletes successively vertices of degree less than or equal to two. If the degree of a vertex is two, both neighbors of the vertex are joined by an edge. The algorithm works without splitting the graph into its biconnected components or using bucket sort to give the adjacency lists a special order.