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We consider an algorithmic problem inspired by the Battleship game. In the variant of the problem that we investigate, there is a unique ship of shape S ⊂ ℤ² which has been translated in the lattice ℤ². We assume that a player has already hit the ship with a first shot and the goal is to sink the ship using as few shots as possible, that is, by minimizing the number of missed shots. While the player knows the shape S, which position of S has been hit is not known. Given a shape S of n lattice points, the minimum number of misses that can be achieved in the worst case by any algorithm is called the Battleship complexity of the shape S and denoted c(S). We prove three bounds on c(S), each considering a different class of shapes. First, we have c(S) ≤ n-1 for arbitrary shapes and the bound is tight for parallelogram-free shapes. Second, we provide an algorithm that shows that c(S) = O(log n) if S is an HV-convex polyomino. Third, we provide an algorithm that shows that c(S) = O(log log n) if S is a digital convex set. This last result is obtained through a novel discrete version of the Blaschke-Lebesgue inequality relating the area and the width of any convex body.

The core problem of discrete tomography, i.e., the faithful reconstruction of an unknown discrete object from projections along a given set of directions, is ill-posed in general. When further constraints are imposed on the object or on the employed directions, uniqueness of the reconstruction can be obtained. It is the case, for example, of convex lattice sets in Z2, for which a theorem by Gardner and Gritzmann assures the faithful reconstruction when suitable sets of directions are considered. It was conjectured that a similar result holds for the class of hv-convex polyominoes. In this paper we are concerned with this conjecture, providing new 4-tuples of discrete directions that do not lead to a unique reconstruction of hv-convex polyominoes, underlining the relevant structural difference with the class of convex sets. Our result is based on the recursive definition of new hv-convex switching components on discrete sets along four directions.

A Mahonian d-function is a Mahonian statistic that can be expressed as a linear combination of vincular pattern functions of length at most d. Babson and Ste- ingrímsson classified all Mahonian 3-functions up to trivial bijections and identified many of them with well-known Mahonian statistics in the literature. We prove a host of Mahonian 3-function equidistributions over permutations in Sn avoiding a single classical pattern in S3. Tools used include block decomposition, Dyck paths and generating functions., QC 20180205

A plane tiling by the copies of a polyomino is called isohedral if every pair of copies in the tiling has a symmetry of the tiling that maps one copy to the other. We show that, for every $n$-omino (i.e., polyomino consisting of n cells), the number of non-equivalent isohedral tilings generated by 90 degree rotations, so called p4-tilings or quarter-turn tilings, is bounded by a constant (independent of n). The proof relies on the analysis of the factorization of the boundary word of a polyomino.

In this paper, we introduce the notion of “rep-cube”: a net of a cube that can be divided into multiple polygons, each of which can be folded into a cube. This notion is inspired by the notion of polyomino and rep-tile; both are introduced by SolomonW. Golomb, and well investigated in the recreational mathematics society. We prove that there are infinitely many distinct rep-cubes. We also extend this notion to doubly covered squares and regular tetrahedra., SCOPUS: ar.j, info:eu-repo/semantics/published

A polyomino is a “simply connected” set of unit squares introduced by Solomon W. Golomb in 1954. Since then, a set of polyominoes has been playing an important role in puzzle society (see, e.g., [3, 1]). In Figure 82 in [1], it is shown that a set of 12 pentominoes exactly covers a cube that is the square root of 10 units on the side. In 1962, Golomn also proposed an interesting notion called “rep-tiles”: a polygon is a reptile of order k if it can be divided into k replicas congruent to one another and similar to the original (see [2, Chap 19]). These notions lead us to the following natural question: is there any polyomino that can be folded to a cube and divided into k polyominoes such that each of them can be folded to a (smaller) cube for some k? That is, a polyomino is a rep-cube of order k if it is a net of a cube, and it can be divided into k polyominoes such that each of them can be folded to a cube. If each of these k polyominoes has the same size, we call the original polyomino regular rep-cube of order k. In this paper, we give an affirmative answer. We first give some regular rep-cubes of order k for some specific k. Based on this idea, we give a constructive proof for a series of regular rep-cubes of order 36gk'^2 for any positive integer k' and an integer g in {2; 4; 5; 8; 10; 50}. That is, there are infinitely many k that allow regular rep-cubes of order k. We also give some non-regular rep-cubes and its variants., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/14768

A plane tiling consisting of congruent copies of a shape is isohedral provided that for any pair of copies, there exists a symmetry of the tiling mapping one copy to the other. We give a O(n*log^2(n))-time algorithm for deciding if a polyomino with n edges can tile the plane isohedrally. This improves on the O(n^{18})-time algorithm of Keating and Vince and generalizes recent work by Brlek, Provençal, Fédou, and the second author.

A polyomino is a “simply connected” set of unit squares introduced by Solomon W. Golomb in 1954. Since then, a set of polyominoes has been playing an important role in puzzle society (see, e.g., [3, 1]). In Figure 82 in [1], it is shown that a set of 12 pentominoes exactly covers a cube that is the square root of 10 units on the side. In 1962, Golomn also proposed an interesting notion called “rep-tiles”: a polygon is a reptile of order k if it can be divided into k replicas congruent to one another and similar to the original (see [2, Chap 19]). These notions lead us to the following natural question: is there any polyomino that can be folded to a cube and divided into k polyominoes such that each of them can be folded to a (smaller) cube for some k? That is, a polyomino is a rep-cube of order k if it is a net of a cube, and it can be divided into k polyominoes such that each of them can be folded to a cube. If each of these k polyominoes has the same size, we call the original polyomino regular rep-cube of order k. In this paper, we give an affirmative answer. We first give some regular rep-cubes of order k for some specific k. Based on this idea, we give a constructive proof for a series of regular rep-cubes of order 36gk'^2 for any positive integer k' and an integer g in {2; 4; 5; 8; 10; 50}. That is, there are infinitely many k that allow regular rep-cubes of order k. We also give some non-regular rep-cubes and its variants.

A plane tiling consisting of congruent copies of a shape is isohedral provided that for any pair of copies, there exists a symmetry of the tiling mapping one copy to the other. We give a O(n log2 n)-time algorithm for deciding if a polyomino with n edges can tile the plane isohedrally. This improves on the O(n18)-time algorithm of Keating and Vince and generalizes recent work by Brlek, Provençal, Fédou, and the second author., SCOPUS: cp.p, info:eu-repo/semantics/published

This paper presents a new partial two-player game, called the cannibal animal game, which is a variant of Tic-Tac-Toe. The game is played on the infinite grid, where in each round a player chooses and occupies free cells. The first player Alice can occupy a cell in each turn and wins if she occupies a set of cells, the union of a subset of which is a translated, reflected and/or rotated copy of a previously agreed upon polyomino P (called an animal). The objective of the second player Bob is to prevent Alice from creating her animal by occupying in each round a translated, reflected and/or rotated copy of P. An animal is a cannibal if Bob has a winning strategy, and a non-cannibal otherwise. This paper presents some new tools, such as the bounding strategy and the punching lemma, to classify animals into cannibals or non-cannibals. We also show that the pairing strategy works for this problem., SCOPUS: ar.j, info:eu-repo/semantics/published

This paper presents a new partial two-player game, called the cannibal animal game, which is a variant of Tic-Tac-Toe. The game is played on the infinite grid, where in each round a player chooses and occupies free cells. The first player Alice can occupy a cell in each turn and wins if she occupies a set of cells, the union of a subset of which is a translated, reflected and/or rotated copy of a previously agreed upon polyomino P (called an animal). The objective of the second player Bob is to prevent Alice from creating her animal by occupying in each round a translated, reflected and/or rotated copy of P. An animal is a cannibal if Bob has a winning strategy, and a non-cannibal otherwise. This paper presents some new tools, such as the bounding strategy and the punching lemma, to classify animals into cannibals or non-cannibals. We also show that the pairing strategy works for this problem., SCOPUS: ar.j, info:eu-repo/semantics/published

In this paper the well-known problem of reconstructing hv-convex polyominoes is considered from a set of noisy data. Differently from the usual approach of Binary Tomography, this leads to a probabilistic evaluation in the reconstruction algorithm, where different pixels assume different probabilities to be part of the reconstructed image. An iterative algorithm is then applied, which, starting from a random choice, leads to an explicit reconstruction matching the noisy data.

This paper presents a computer-aided geometric design approach to realize a new genre of 3D puzzle, namely the 3D Polyomino puzzle. We base our puzzle pieces on the family of 2D shapes known as polyominoes in recreational mathematics, and construct the 3D puzzle model by covering its geometry with polyomino-like shapes. We first apply quad-based surface parametrization to the input solid, and tile the parametrized surface with polyominoes. Then, we construct a nonintersecting offset surface inside the input solid and shape the puzzle pieces to fit inside a thick shell volume. Finally, we develop a family of associated techniques for precisely constructing the geometry of individual puzzle pieces, including the ring-based ordering scheme, the motion space analysis technique, and the tab and blank construction method. The final completed puzzle model is guaranteed to be not only buildable, but also interlocking and maintainable.

This paper presents a computer-aided geometric design approach to realize a new genre of 3D puzzle, namely the 3D Polyomino puzzle. We base our puzzle pieces on the family of 2D shapes known as polyominoes in recreational mathematics, and construct the 3D puzzle model by covering its geometry with polyomino-like shapes. We first apply quad-based surface parametrization to the input solid, and tile the parametrized surface with polyominoes. Then, we construct a nonintersecting offset surface inside the input solid and shape the puzzle pieces to fit inside a thick shell volume. Finally, we develop a family of associated techniques for precisely constructing the geometry of individual puzzle pieces, including the ring-based ordering scheme, the motion space analysis technique, and the tab and blank construction method. The final completed puzzle model is guaranteed to be not only buildable, but also interlocking and maintainable.

This paper presents a computer-aided geometric design approach to realize a new genre of 3D puzzle, namely the 3D Polyomino puzzle. We base our puzzle pieces on the family of 2D shapes known as polyominoes in recreational mathematics, and construct the 3D puzzle model by covering its geometry with polyomino-like shapes. We first apply quad-based surface parametrization to the input solid, and tile the parametrized surface with polyominoes. Then, we construct a nonintersecting offset surface inside the input solid and shape the puzzle pieces to fit inside a thick shell volume. Finally, we develop a family of associated techniques for precisely constructing the geometry of individual puzzle pieces, including the ring-based ordering scheme, the motion space analysis technique, and the tab and blank construction method. The final completed puzzle model is guaranteed to be not only buildable, but also interlocking and maintainable.

We study the combinatorial properties and the problem of generating exhaustively double square tiles, i.e. polyominoes yielding two distinct periodic tilings by translated copies such that every polyomino in the tiling is surrounded by exactly four copies. We show in particular that every prime double square tile may be obtained from the unit square by applying successively some invertible operators on double squares. As a consequence, we prove a conjecture of Provençal and Vuillon (2008) [17] stating that these polyominoes are invariant under rotation by angle π (pi).

It has been proved that, among the polyominoes that tile the plane by translation, the so-called squares tile the plane in at most two distinct ways. In this paper, we focus on double squares, that is, the polyominoes that tile the plane in exactly two distinct ways. Our approach is based on solving equations on words, which allows us to exhibit properties about their shape. Moreover, we describe two infinite families of double squares. The first one is directly linked to Christoffel words and may be interpreted as segments of thick straight lines. The second one stems from the Fibonacci sequence and reveals some fractal features.

Cette thèse, constituée d'une série d'articles, considère des questions issues de la géométrie discrète en les traitant du point de vue de la combinatoire des mots qui s'avère un outil puissant et approprié pour les résoudre. Nous utilisons les mots soit pour représenter un chemin dans Z2 ou Z3, soit pour coder la suite des virages d'un chemin ou le contour d'une figure discrète fermée. Parmi les thèmes abordés, on compte les pavages du plan par polyominos, la notion de complexité en facteurs palindromes et la génération de droites discrètes 3D. La première partie concerne les pavages du plan où nous étudions le nombre de pavages réguliers du plan par une tuile carrée, c'est-à-dire une tuile ayant quatre tuiles adjacentes identiques. Il s'avère que certaines tuiles carrées pavent le plan de deux façons distinctes et elles sont appelées doubles carrées. Nous démontrons d'abord qu'il y a au plus deux tels pavages réguliers par une tuile carrée. Ensuite, nous considérons deux familles particulières de tuiles doubles carrées : les tuiles de Christoffel et les tuiles de Fibonacci. Ces deux familles décrivent les plus petits exemples de tuiles doubles carrées et peuvent être définies à partir des mots de Christoffel et du mot de Fibonacci par des règles de substitution et de concaténation. Les tuiles de Fibonacci définissent aussi une fractale, obtenue par un chemin auto-évitant, dont nous avons calculé plusieurs statistiques, comme le rapport de l'aire de la fractale sur l'aire de son enveloppe convexe. Dans l'article suivant, nous démontrons que tout double carré indécomposable est invariant sous une rotation de 180 degrés. Cette propriété géométrique est équivalente au fait que le mot de contour de la tuile se factorise en un produit de palindromes. Notre preuve repose sur une méthode de génération exhaustive des tuiles doubles carrées. La deuxième partie concerne la complexité palindromique - le nombre de facteurs palindromes distincts -, un sujet propre à la combinat

Les polyominos sont souvent représentés par des mots de quatre lettres ou des mots de changements de direction décrivant leur contour. La combinatoire des mots classique y joue donc un rôle descriptif important, particulièrement dans le choix d'un représentant canonique. Les mots de Lyndon fournissent, de façon naturelle, un tel représentant. Une approche systématique pour le calcul de propriétés des polyominos, basée sur une version originale d'une discrétisation du théorème de Green classique en calcul bivarié, est élaborée. Ceci nous a naturellement amené à analyser les propriétés géométriques d'ensembles du réseau discret de rondeur maximale. Pour une taille donnée, ces ensembles minimisent le moment d'inertie par rapport à un axe passant par leur centre de gravité. Nous introduisons la notion de quasi-disque et montrons entre autres que ces ensembles minimaux sont des poIyominos fortement-convexes. Nous développons également un algorithme permettant de les engendrer systématiquement. Un autre aspect concerne des propriétés sur les contours d'ensembles discrets donnant lieu à une nouvelle démonstration d'un résultat de Daurat et Nivat sur les points dits saillants et rentrants d'un polyomino. Nous présentons également une généralisation de ce résultat aux réseaux hexagonaux et montrons que le résultat est faux pour les autres réseaux semi-réguliers. Nous poursuivons par l'introduction d'opérations de mélange spéciaux sur des mots décrivant des chemins discrets selon la suite de leurs changements de direction. Ces opérations de mélange permettent d'engendrer des courbes fractales du type courbe de dragon et d'analyser certains de leurs invariants. Finalement, une généralisation aux dimensions supérieures des algorithmes précédents basés sur le théorème de Green discret, est présentée. Plus particulièrement, nous développons une version discrète du théorème de Stokes basée sur des familles de poids sur les hypercubes de dimension k dans l'espace discret Zn, k ≤ n.

It has been proved that, among the polyominoes that tile the plane by translation, the so-called squares tile the plane in at most two distinct ways. In this paper, we focus on double squares, that is, the polyominoes that tile the plane in exactly two distinct ways. Our approach is based on solving equations on words, which allows us to exhibit properties about their shape. Moreover, we describe two infinite families of double squares. The first one is directly linked to Christoffel words and may be interpreted as segments of thick straight lines. The second one stems from the Fibonacci sequence and reveals some fractal features.