<p>In this paper, we extend the concept of <i>k</i>-distance total domination to the concept of <i>L</i>-distance total domination, which is to find a minimum vertex set <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(D\subseteq V\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>D</mi> <mo>⊆</mo> <mi>V</mi> </mrow> </math></EquationSource> </InlineEquation> such that each vertex <i>v</i> of the graph <i>G</i> is at a distance <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(0&lt;d(v,u)\leqslant a_v\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>&lt;</mo> <mi>d</mi> <mrow> <mo stretchy="false">(</mo> <mi>v</mi> <mo>,</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>⩽</mo> <msub> <mi>a</mi> <mi>v</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> from some vertex <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(u\in D\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>u</mi> <mo>∈</mo> <mi>D</mi> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(a_v\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>a</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation> is an arbitrary positive integer assigned to <i>v</i>, and <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(L=\{a_{v}|~v\in V(G)\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mo>=</mo> <mo stretchy="false">{</mo> <msub> <mi>a</mi> <mi>v</mi> </msub> <mo stretchy="false">|</mo> <mspace width="3.33333pt" /> <mi>v</mi> <mo>∈</mo> <mi>V</mi> <mrow> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">}</mo> </mrow> </math></EquationSource> </InlineEquation>. We then compute the exact values of the <i>L</i>-distance total domination numbers of paths and cycles. Finally, by constructing a proper order of the vertices and using a labeling method, we provide an <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(O(n^2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>O</mi> <mo stretchy="false">(</mo> <msup> <mi>n</mi> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> time algorithm to find a minimum <i>L</i>-distance total dominating set of a block graph, a superclass of trees. Since <i>k</i>-distance total domination is a special form of <i>L</i>-distance total domination, the above algorithm can also determine the <i>k</i>-distance total domination number of a block graph.</p>

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L-Distance Total Domination and a Polynomial Algorithm in Block Graphs

  • Yancai Zhao,
  • Zuosong Liang

摘要

In this paper, we extend the concept of k-distance total domination to the concept of L-distance total domination, which is to find a minimum vertex set \(D\subseteq V\) D V such that each vertex v of the graph G is at a distance \(0<d(v,u)\leqslant a_v\) 0 < d ( v , u ) a v from some vertex \(u\in D\) u D , where \(a_v\) a v is an arbitrary positive integer assigned to v, and \(L=\{a_{v}|~v\in V(G)\}\) L = { a v | v V ( G ) } . We then compute the exact values of the L-distance total domination numbers of paths and cycles. Finally, by constructing a proper order of the vertices and using a labeling method, we provide an \(O(n^2)\) O ( n 2 ) time algorithm to find a minimum L-distance total dominating set of a block graph, a superclass of trees. Since k-distance total domination is a special form of L-distance total domination, the above algorithm can also determine the k-distance total domination number of a block graph.