摘要：A simple graph is P4-indifferent if it admits a total order its nodes such that every chordless path with nodes a, b, c, d and edges ab, bc, cd has a b > c > d. P4-indifferent graphs generalize indifferent graphs and are perfectly orderable. Recently, Hoang, Maray and Noy gave a characterization of P4-indifferent graphs in terms of forbidden induced subgraphs. We clarify their proof and describe a linear time algorithm to recognize P4-indifferent graphs. When the input is a P4-indifferent graph, then the algorithm computes an order Key words: P4-indifference, linear time, recognition, modular decomposition.
