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Periods in strings
 Journal of Combinatorial Theory, Series A
, 1981
"... A survey is presented of some methods and results on counting words that satisfy various restrictions on subwords (i.e., blocks of consecutive symbols). Various applications to commafree codes, games, pattern matching, and other subjects are indicated. The emphasis is on the unified treatment of th ..."
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Cited by 78 (0 self)
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A survey is presented of some methods and results on counting words that satisfy various restrictions on subwords (i.e., blocks of consecutive symbols). Various applications to commafree codes, games, pattern matching, and other subjects are indicated. The emphasis is on the unified treatment of those topics through the use of generating functions. 1.
Robust Universal Complete Codes for Transmission and Compression
 Discrete Applied Mathematics
, 1996
"... Several measures are defined and investigated, which allow the comparison of codes as to their robustness against errors. Then new universal and complete sequences of variablelength codewords are proposed, based on representing the integers in a binary Fibonacci numeration system. Each sequence is ..."
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Cited by 10 (4 self)
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Several measures are defined and investigated, which allow the comparison of codes as to their robustness against errors. Then new universal and complete sequences of variablelength codewords are proposed, based on representing the integers in a binary Fibonacci numeration system. Each sequence is constant and need not be generated for every probability distribution. These codes can be used as alternatives to Huffman codes when the optimal compression of the latter is not required, and simplicity, faster processing and robustness are preferred. The codes are compared on several "reallife" examples. 1. Motivation and Introduction Let A = fA 1 ; A 2 ; \Delta \Delta \Delta ; An g be a finite set of elements, called cleartext elements, to be encoded by a static uniquely decipherable (UD) code. For notational ease, we use the term `code' as abbreviation for `set of codewords'; the corresponding encoding and decoding algorithms are always either given or clear from the context. A code i...
Combinatorial problems motivated by commafree codes
 J. Combin. Des
, 2004
"... Abstract In the paper some combinatorial problems motivated by commafree codes are considered. We describe these problems, give the most significant known results and methods used, present some new results and formulate open problems. ..."
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Abstract In the paper some combinatorial problems motivated by commafree codes are considered. We describe these problems, give the most significant known results and methods used, present some new results and formulate open problems.
Symmetry breaking in constraint satisfaction with graphisomorphism commafree codes
 Proc. of AI&M 2004. 2004. http://www.informatik.unitrier.de/~ley/db/conf/amai/amai2004.html
"... Abstract. In recent years, symmetry breaking for constraint satisfaction problems (CSPs) has attracted considerable attention. Various general schemes have been proposed to eliminate symmetries. In general, these schemes may take exponential space or time to eliminate all the symmetries. We identify ..."
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Abstract. In recent years, symmetry breaking for constraint satisfaction problems (CSPs) has attracted considerable attention. Various general schemes have been proposed to eliminate symmetries. In general, these schemes may take exponential space or time to eliminate all the symmetries. We identify several classes of CSPs that encompass many practical problems and for which symmetry breaking for various forms of value or variable interchangeability is tractable using dedicated search procedures. We also show the limits of efficient symmetry breaking for such dominancedetection schemes by proving intractability results for some classes of CSPs. 1
Restrictions and Generalizations on CommaFree Codes
"... A significant sector of coding theory is that of commafree coding; that is, codes which can be received without the need of a letter used for word separation. The major difficulty is in finding bounds on the maximum number of commafree words which can inhabit a dictionary. We introduce a new class ..."
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A significant sector of coding theory is that of commafree coding; that is, codes which can be received without the need of a letter used for word separation. The major difficulty is in finding bounds on the maximum number of commafree words which can inhabit a dictionary. We introduce a new class called a selfreflective commafree dictionary and prove a series of bounds on the size of such a dictionary based upon word length and alphabet size. We also introduce other new classes such as selfswappable commafree codes and commafree codes in q dimensions and prove preliminary bounds for these classes. Finally, we discuss the implications and applications of combining these original concepts, including their implications for the NPcomplete Post Correspondence Problem. 1
A CHARACTERIZATION OF MAXIMUM INDEPENDENT SETS OF DE BRUIJN GRAPHS
, 905
"... Abstract. The de Bruijn graph B(d, 3) consists of all strings of length 3, taken from an alphabet of size d, with edges between words which are distinct substrings of a word of length 4. We give an inductive characterization of the maximum independent sets of the de Bruijn graphs B(d, 3) and for the ..."
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Abstract. The de Bruijn graph B(d, 3) consists of all strings of length 3, taken from an alphabet of size d, with edges between words which are distinct substrings of a word of length 4. We give an inductive characterization of the maximum independent sets of the de Bruijn graphs B(d, 3) and for the de Bruijn graph with loops removed, for all d. We derive a recurrence relation for their number. 1.