European Symposium on Algorithms – ESA University of Ljubljana Faculty of Computer and Information Science European Symposium on Algorithms – ESA ESA 2016 Conference review Preparation: Ilcho Koteski

What is ESA? ESA is Annual European Symposium on Algorithms Short history The first ESA was held back in 1993 and since then it is one of the premier conferences on algorithms. It covers research in efficient algorithms and data structures in computer science, discrete applied mathematics, operations research and mathematical programming. Starting with ESA 2002, WAE (Workshop on Algorithm Engineering) was also incorporated into ESA. Since then the symposium has two tracks: Design and Analysis Track (Design and mathematical analysis of algorithms) Engineering and Application Track (Real-world applications, engineering and experimental analysis of algorithms) Each track has its own program committee. Papers are submitted to a particular track, but the committees have the right to move papers between tracks.

When and where was last ESA? The last ESA was held on 22 August – 24 August 2016, in Aarhus – Denmark It was its 24th annual edition Part of ALGO 2016 Conference 76 papers were accepted Including these three: Probabilistic Routing for On-Street Parking Search Approximation and Hardness of Token Swapping Faster External Memory LCP Array Construction

1. Probabilistic Routing for On-Street Parking Search Problem for solving: Street parking NP-complete problem Hamiltonian path Three parameters taken into account: Probability of finding parking spot Walking distance Duration c(P)= 2(λ * distance + (1- λ) duration ) , λ E [0, 1] Two algorithms as a solutions Branch and Bound Heuristic Search -> cost measure = 1.3* cost measure (Branch and Bound)

2. Approximation and Hardness of Token Swapping We have a graph G = (V, E) ; V= {1,...,n} Every vertex has a token assigned T1,...,Tn Problem for solving: How to find the shortest sequence of token swaps such that token Ti is placed on vertex i. More generalized version – color matching. NP-complete problem They prove that this can be solved in exponential time 2O(n log n) based on breadth-first search in an auxiliary graph. 4-Approximation algorithm Approximation algorithm with approximation factor: 4 on general graphs 2 on trees Constant k such that every polynomial time approximation algorithm has approximation factor of at least k. Hardness: APX-hard

3. Faster External Memory LCP Array Construction Suffix array and LCP(Longest Common Prefix) array Memory limitations (Data too big for RAM memory) Problem for solving: How the suffix array to be augmented to LCP array in external memory Known algorithm: LCPscan Two Semi-External memory algorithms transformed into Fully External memory algorithms which compute LCP in: Sparse-Φ : SuccinctIrreducible:

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