Detecting leftmost maximal periodicities
Discrete Applied Mathematics - Combinatorics and complexity
How many squares can a string contain?
Journal of Combinatorial Theory Series A
Finding Maximal Repetitions in a Word in Linear Time
FOCS '99 Proceedings of the 40th Annual Symposium on Foundations of Computer Science
A simple proof that a word of length n has at most 2n distinct squares
Journal of Combinatorial Theory Series A
A note on the number of squares in a word
Theoretical Computer Science
A Continuous d-Step Conjecture for Polytopes
Discrete & Computational Geometry
A d-step approach for distinct squares in strings
CPM'11 Proceedings of the 22nd annual conference on Combinatorial pattern matching
On the structure of run-maximal strings
Journal of Discrete Algorithms
On the maximum number of cubic subwords in a word
European Journal of Combinatorics
A computational framework for determining run-maximal strings
Journal of Discrete Algorithms
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Fraenkel and Simpson conjectured in 1998 that the number of distinct squares in a string is at most its length. Kolpakov and Kucherov conjectured in 1999 that the number of runs in a string is also at most its length. Since then, both conjectures attracted the attention of many researchers and many results have been presented, including asymptotic lower bounds for both, asymptotic upper bounds for runs, and universal upper bounds for distinct squares in terms of the length. In this survey we point to the combined role played by the length and the number of distinct symbols of the string in both problems. Let us denote @s"d(n), respectively @r"d(n), the maximum number of distinct primitively rooted squares, respectively runs, over all strings of length n containing exactly d distinct symbols. We study both functions @s"d(n) and @r"d(n) and revisit earlier results and conjectures with the (d,n)-parameterized approach. The parameterized approach reveals regularities for both @s"d(n) and @r"d(n) which have been computationally verified for all known values. In addition, the approach provides a computationally efficient framework. We were able to determine all previously known @r"2(n) values for n@?60 in a matter of hours, confirming the results reported by Kolpakov and Kucherov, and were able to extend the computations up to n=74. Similarly, we were able to extend the computations up to n=70 for @s"2(n). We point out that @s"2(33)=70. The computations also reveal the existence of unexpected binary run-maximal string of length 66 containing a quadruple of identical symbols aaaa.