The book discusses solutions to the original problems of international and national olympiads in computer science and programming for schoolchildren and students. Tasks are grouped by topic: maximum flow, minimum spanning tree, trees, hidden graphs, strategy games, Young's scoreboard. At the beginning of each chapter, the necessary theoretical material on the topic is succinctly but accessible, then the condition, solution idea and description of a specific implementation in the Pascal programming language are given for each problem. For schoolchildren, students and their teachers.