期刊名称：Electronic Colloquium on Computational Complexity
印刷版ISSN：1433-8092
出版年度：1998
卷号：1998
出版社：Universität Trier, Lehrstuhl für Theoretische Computer-Forschung
摘要：TSP(1,2), the Traveling Salesman Problem with distances 1 and 2, is
the problem of finding a tour of minimum length in a complete
weighted graph where each edge has length 1 or 2. Let do satisfy
0do12 . We show that TSP(1,2) has no PTAS on the set of
instances where the density of the subgraph spanned by the edges with
length 1 is bounded below by do. We also show that LONGEST PATH
has no PTAS on the set of instances with density bounded below by
do for all 0do12 .
