The L(2,1) -Labeling of Outerplane Graphs

Abstract:

      It is proved that an outerplane graph contains no subdivision of K₄ or K_2,3. Let G be an outerplane graph. We show that the L(2,1) -labeling number λ(G)≤△(G) + 9 , where △(G) is the maximum degree of vertices in G .