Characterizing r-perfect codes in direct products of two and three cycles

  • Authors:
  • Janja Jerebic;Sandi Klavžar;Simon Špacapan

  • Affiliations:
  • Department of Mathematics and Computer Science, PEF, University of Maribor, Koroška cesta 160, 2000 Maribor, Slovenia;Department of Mathematics and Computer Science, PEF, University of Maribor, Koroška cesta 160, 2000 Maribor, Slovenia;University of Maribor, FME, Smetanova 17, 2000 Maribor, Slovenia

  • Venue:
  • Information Processing Letters
  • Year:
  • 2005

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Abstract

An r-perfect code of a graph G=(V,E) is a set C@?V such that the r-balls centered at vertices of C form a partition of V. It is proved that the direct product of C"m and C"n (r=1, m,n=2r+1) contains an r-perfect code if and only if m and n are each a multiple of (r+1)^2+r^2 and that the direct product of C"m, C"n, and C"@? (r=1, m,n,@?=2r+1) contains an r-perfect code if and only if m, n, and @? are each a multiple of r^3+(r+1)^3. The corresponding r-codes are essentially unique. Also, r-perfect codes in C"2"rxC"n (r=2, n=2r) are characterized.