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Gracefulness of Unconnected Graphs(P1∨Pn)∪Gr,(P1∨Pn)∪(P3r) and Wn∪St(m)

CAI Hua1, WEI Lixia2, LV Xianrui1   

  1. 1. Institute of Mathematics, Jilin University, Changchun 130012, China;2. Department of Foundation, North China Institute of Science and Technology, Beijing 101601, China
  • Received:2006-08-22 Revised:1900-01-01 Online:2007-07-26 Published:2007-07-26
  • Contact: WEI Lixia

Abstract: The present paper deals with the gracefulness of three kinds of unconnected graphs ((P1∨Pn)∪Gr,(P1∨Pn)∪(P3r) and Wn∪St(m), and proves the following results: for positive integers n and m, let s=[n/2], r=s-1, Gr be a graceful graph with redges, if n≥4, then the unconnected graphs (P1∨Pn)∪Gr,(P1∨Pn)∪(P3r) are both graceful graphs; if n≥3andm≥s, then the unconnected graph Wn∪St(m) is a graceful graph, where Pn is an nvertex path, Kn is an nvertex complete graph, nis the complement of graph Kn, graph G1∨G2 is the join graph of G1 and G2, Wnis an (n+1)vertex wheel graph and St(m)is an (m+1) vertex star tree.

Key words: graceful graph, graceful label, unconnected graph

CLC Number: 

  • O157.9