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- Luitpold Babel, Gottfried Tinhofer
- ZOR - Meth. & Mod. of OR
- 1990

A method to solve the maximum clique problem based on an unconstmin~ quadratic zero-one programming fo~ulation is presented. A branch and bound algorithm for unconstrained quadratic zero-one programming is given that uses a technique to dynamically select variables for the ordering of the branching tree. Dynamic variable selection is equivalent to vertex… (More)

- Gottfried Tinhofer
- Computing
- 1986

Two graphsG andG′ having adjacency matricesA andB are called ds-isomorphic iff there is a doubly stochastic matrixX satisfyingXA=BX.Ds-isomorphism is a relaxation of the classical isomorphism relation. In section 2 a complete set of invariants with respect tods-isomorphism is given. In the case whereA=B (ds-automorphism) the main question is: For which… (More)

- Gottfried Tinhofer
- Discrete Applied Mathematics
- 1989

This paper deals with graph invariants and stabilization procedures. We consider colored graphs and their automorphisms and we discuss the isomorphism problem for such graphs. Various global and local isomorphism invariants are introduced. We study canonical numberings, invariant partitions, stable and equitable partitions and algorithms for stabilizing… (More)

- Gottfried Tinhofer
- Discrete Applied Mathematics
- 1991

- Sergei Evdokimov, Ilia N. Ponomarenko, Gottfried Tinhofer
- Discrete Mathematics
- 2000

In this paper we introduce and investigate a new class of graphs called algebraic forests for which isomorphism testing can be done in time O(n3 log n). The class of algebraic forests admits a membership test of the same complexity, it includes cographs, trees and interval graphs, and even a joint superclass of the latter two, namely, rooted directed path… (More)

- Luitpold Babel, Gottfried Tinhofer
- Discrete Applied Mathematics
- 1994

- Winfried Hochstättler, Gottfried Tinhofer
- Computing
- 1995

In a recent series of articles R. Jamison and S. Olariu developed, starting from an extension of the notion of a cograph, a theory of the decomposition of graphs intoP 4-connected components. It turned out in their work that the algorithmic idea to exploit the unique tree structure of cographs can be generalized to graphs with simpleP 4-structure. In this… (More)

- Gottfried Tinhofer, Helmut Schreck
- Computing
- 1984

This paper deals with a new method of coding unlabeled trees, the resulting code being a string of integers. For a tree onn vertices both the coding and the decoding algorithm work in time 0(n). Givenn the “mean length” of code strings is shorter than with other existing integer string codes. The new coding method is used to derive an algorithm for… (More)

- Gottfried Tinhofer, Helmut Schreck
- Inf. Process. Lett.
- 1986