Handbook of formal languages, vol. 1
On the number of Abelian square-free words on four letters
Discrete Applied Mathematics
Unavoidable sets of words of uniform length
Information and Computation
Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
Abelian Squares are Avoidable on 4 Letters
ICALP '92 Proceedings of the 19th International Colloquium on Automata, Languages and Programming
Maximal abelian square-free words of short length
Journal of Combinatorial Theory Series A
Applied Combinatorics on Words (Encyclopedia of Mathematics and its Applications)
Applied Combinatorics on Words (Encyclopedia of Mathematics and its Applications)
Theoretical Computer Science
On shortest crucial words avoiding abelian powers
Discrete Applied Mathematics
On the complexity of deciding avoidability of sets of partial words
Theoretical Computer Science
Minimum number of holes in unavoidable sets of partial words of size three
IWOCA'10 Proceedings of the 21st international conference on Combinatorial algorithms
Number of holes in unavoidable sets of partial words I
Journal of Discrete Algorithms
| Hi-index | 0.01 |
We introduce the notion of a set of prohibitions and give definitions of a complete set and a crucial word with respect to a given set of prohibitions. We consider three special sets which appear in different areas of mathematics and for each of them examine the length of a crucial word. One of these sets is proved to be incomplete. The problem of determining lengths of words that are free from a set of prohibitions is shown to be NP-complete, although the related problem of whether or not a given set of prohibitions is complete is known to be effectively solvable.