Looking for a challenge?

Contest tasks say a lot about the quality of a programming competition. They should be original, engaging and of different levels of difficulty. Finding a solution should cause the contestant to feel great satisfaction, whereas being unable to solve a given task should encourage an individual to broaden their knowledge and develop new skills. This book contains the best tasks from algorithmic and programming competitions organized or co-organized by the University of Warsaw, together with their exemplary solutions. The selection of the tasks was undertaken by people who have played significant roles in the history of Polish algorithmic and programming competitions as their participants or organizers. All of the authors of texts presented in this book are closely affiliated with the Faculty of Mathematics, Informatics and Mechanics at the University of Warsaw, whether as former or current students or as academic staff. Each of the tasks presented and discussed in this book was used during one of the following events: Polish Olympiad in Informatics, Junior Polish Olympiad in Informatics, Polish Olympiad in Informatics Training Camp, Central European Olympiad in Informatics, Polish Collegiate Programming Contest, Algorithmic Engagements.

Preface to the Second Edition 9 Introduction 13 Szymon Acedański Ants 22 Marcin Andrychowicz Hyperclock 29 Marcin Andrychowicz Fishes 35 Piotr Chrząstowski Pilots 45 Piotr Chrząstowski Skiers 57 Marek Cygan Barricades 67 Marek Cygan Travel Agency 72 Tomasz Czajka Mushrooms 81 Tomasz Czajka Sweets 87 Krzysztof Diks Coding of Permutations 95 Krzysztof Diks Rooks 106 Andrzej Gąsienica-Samek Monkeys 112 Tomasz Idziaszek Plotter 120 Tomasz Idziaszek Termites 127 Grzegorz Jakacki Window 136 Grzegorz Jakacki Altars 142 Tomasz Kociumaka Axes of Symmetry 155 Tomasz Kociumaka Leonardo Numbers 161 Eryk Kopczyński Ritual 174 Eryk Kopczyński Questions 180 Marcin Kubica Chocolate 190 Marcin Kubica Fibonacci Sums 197 Tomasz Kulczyński The Search 206 Tomasz Kulczyński Hashing 213 Jakub Łącki Afternoon Tea 220 Jakub Łącki Kangaroos 224 Krzysztof Onak Sums 239 Krzysztof Onak Superknight 244 Jakub Pachocki Ice Skates 255 Jakub Pachocki Termites 2 260 Paweł Parys Cave 268 Paweł Parys Shuffle 276 Jakub Pawlewicz Game of Tokens 281 Jakub Pawlewicz Straight Lines 285 Marcin Pilipczuk Guilds 297 Marcin Pilipczuk Reconstruction of Byteland 306 Michał Pilipczuk Army Training 311 Michał Pilipczuk Riddle 319 Jakub Radoszewski Fuel 327 Jakub Radoszewsk Ploughing 334 Wojciech Rytter Canoes 342 Wojciech Rytter Painter’s Studio 346 Krzysztof Stencel Triangles 356 Krzysztof Stencel Triangles 2 357 Krzysztof Stencel Circular Game 364 Wojciech Śmietanka Byteland 372 Wojciech Śmietanka Cakes 378 Tomasz Waleń Building Blocks 383 Tomasz Waleń Matching 391 Jakub Wojtaszczyk Party 399 Jakub wojtaszczyk Dice 407 Filip Wolski Two Parties 413 Filip Wolski Guesswork 420