Features of the four-level approach to training for student Olympiads in computer science

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Uzhhorod National University

Features of the four-level approach to training for student olympiads in computer science

S.D. Vapnichnyi Senior Lecturer

Abstract

The article proposes elements of the methodological system of training students for computer science Olympiads (CSO), which covers four levels: basic, medium, high and advanced. For each of the levels, a list of topics is given; for some topics there are proposed assessment tasks, that can be used to determine the student's readiness. Also for each level the sets of tasks on eolymp.com and codeforces.com are offered. To increase the effectiveness of the proposed approach, it is recommended that students, starting from the medium level, participate in various competitions and Olympiads, which give many motivating impulses to master programming. High and advanced levels include own topics and tasks as well. Besides, the paper formulates the requirements that were the basis for the selection of tasks by topics and separation of the proposed levels. In particular, there are proposed the following requirements for tasks: availability of interesting plot, making curiosity for students, illustrativeness, connectivity and diversity. The construction of task systems takes into account the didactic and methodological requirements that determine the pedagogical expediency of their use. The model of the process of creating a tasks system, which consists of analytical, design and technological stages, is described.

The proposed approach methodology was successfully used in teaching students of Uzhhorod specialized boarding school with in-depth study of certain subjects (UzhSBSwiDSCS), at summer and winter programming schools in Kremenchug and summer programming schools in Khust. Many students of UzhSBSwiDSCS studied on the basis of this approach, participated in competitions and became winners of various stages of the All-Ukrainian Student Olympiad in Informatics. The mentioned approach has been successfully tested in distance learning. Key words: computer science, elements of methodological system, Olympiad, programming schools.

Introduction of the issue. The global IT industry is growing rapidly and needs more and more employees. These workers do not need to build large factories, as in the days of industrialization, but just ordinary office space and computer equipment. But the training of such a specialist is much more difficult than an employee in the industry. This training should start at school. Various competitions, tournaments and Olympiads contribute to the development of motivation to engage in programming in the initial stages. Current state of the issue. There is a number of publications related to this topic. In [1] theoretical information on three main functions of teaching programming is highlighted and presented: general educational, developmental and upbringing. It is stated that the general educational function of teaching programming in schools is to form students' knowledge of the fundamental concepts and paradigms of programming and the formation of students' programming skills and abilities. The developmental function is to develop students' algorithmic thinking style, intellectual qualities and creative abilities, the formation of students' ability to see the problem at different levels of detail, the ability to use programming to solve practical problems. The upbringing function is to form in students such qualities as pedantry, discipline, accuracy, internal control, perseverance, awareness of personal responsibility for the results of their work, the desire for self-affirmation through creative activities, ability to work both individually and collectively, systematic learning.

In [2] three components of preparing students for Olympiads in informatics are highlighted: diagnostic-motivational, content-theoretical and procedural- activity (competitive-training). It is stated that diagnostic-motivational one is aimed at identifying students capable of programming and solving non-standard problems, motivating students to in-depth study of this section of computer science. Content-theoretical component consists of 2 subcomponents: learning a specific programming language and solving logical, non-standard problems using simple programming methods (array search, use of mathematical formula etc.); study of basic Olympiad algorithms and their application in solving problems. Procedural-activity (competitive-training) component is aimed at consolidating theoretical material, its application to solving Olympiad tasks of different levels of complexity, participation in Olympiads, contests, tournaments, writing computer programs. On the basis of the specified components the author's approach to training for Olympiads is offered.

In [3] the main stages of students training for participation in competitions are indicated and the classification of Internet resources that can be used in the educational process is considered. In [4] it is described in detail the method of conducting two lessons on the topics: wave algorithm for finding the shortest path in the maze and ordering tabular quantities. In [5] a brief overview of systems of training for the Olympiads in informatics in some countries is provided. In [6] the scheme consisting of seven stages is proposed to solve the Olympiad problem. The analysis of the considered sources shows that the authors do not offer a level differentiation of methods with a description of topics and a list of corresponding tasks, that is seen as a shortcoming. Accordingly, this article proposes a methodology of training for Olympiads, taking into account the division at the levels and describes its features. Aim of research is to develop elements of the methodological system, that provide a four-level approach to the training for Olympiad in informatics for secondary school students, to describe in detail the topics for each of the levels, to select tasks for each topic.

Methodology: аnalysis and generalization of experience of long-term practical training students for the Olympiads in informatics, experience of other coaches, selection and systematization of Olympiad tasks of different levels of complexity, work with scientific and scientific-methodological sources, systematic approach to teaching computer science.

Scientific novelty: there have been developed elements of the methodological system, that provide a four-level approach to the training for Olympiad in informatics for secondary school students; the development contains classified topics and tasks that correspond to each of the four proposed levels. These elements of methodology has been tested and proved to be quite effective in teaching students programming and training for the Olympiads in informatics.

Results and discussion. In training for the Olympiads in informatics, we will

highlight the following requirements for the selection of tasks by topics and determine the levels: 1) availability of interesting plot and making curiosity for students (to gain the attention of students and engage them in Olympiad informatics, distracting them from the gadgets with which they spend more and more time); 2) illustrativeness (so that it is possible to conveniently depict the task, which will allow students to better see it and possibly reduce it to an isomorphic or similar task); 3) connectivity (important topics are continued at the next level and require quality training in the previous material; for example, at the second level students study the general concepts of graphs and input / output of relevant data structures, the third level is used in the study of in-depth search, which is being used at the fourth level in finding the component of strong connectivity of the graph); 4) diversity (the system of tasks takes into account the presence of different types of thinking, types of memory etc.). At task systems building, the requirements that determine the pedagogical expediency of their use are taken into account: didactic, reflecting the relevant traditional and specific principles of teaching, and methodological that take into account the features of informatics as a subject and science. methodical olympiad readiness

The model of the process of creating a system of tasks (as a set of tasks, in some way related to each other and having several levels of organization in relation to consistent subordination) consists of the following stages: 1) analytical (analysis of educational material meaning, formulation of goals and determination their mutual compliance, selection of content); 2) design (choice of methods and techniques, determination of forms of presentation of educational material, methods of its presentation); 3) technological (technical creation of task systems in accordance with the requirements).

It is proposed to teach students programming according to a scheme that provides four levels: basic, medium, high and advanced.

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Fig. 1. Scheme of training on four levels

Elements of the methodology of teaching the basics of programming, as well as literature that covers the basic level, are given in [7]. In the process of studying a certain topic, students are grouped into different age groups according to the method of Valentyn Melnyk, who has the title of People's Teacher of Ukraine [8]. The main factor in the formation of such groups is not age, but the degree of mastery of topics that corresponds to a certain level.

The basic level allows mastering the basics of programming and includes topics such as linear, conditional and cyclic constructions, working with strings and arrays, bit operations, procedures and functions. Each topic includes a number of different subtopics. In particular, the topic "Linear structures" includes the following subtopics:

example of a simple program;

constants and variables;

types of variables;

assignment operator;

arithmetic in C ++, arithmetic expressions and operations;

input, output to the console in the style of C and C ++ (printf, scanf, cin, cout threads);

formatted input and output to the console.

The selection of tasks for these subtopics is given in Table 1.

Table 1 Topics and tasks covered by the basic level

Fig. 2. General scheme of work on each topic

Each topic is processed according to the scheme shown in Figure 2.

The scheme connects the following sequence of actions that will allow effective teaching:

Lecturing of the new topic material, answers to students' questions after the lecture.

Providing presentations and other supporting materials.

Analysis of the tasks that caused the greatest difficulties for students at the beginning of a new class before presentation of new material.

Providing a large number of practical tasks on a new topic and the opportunity to solve them during the week. The easier the topic, the more tasks are provided. In particular, there may be hundreds of such tasks on the first topics of the basic level. Verification is carried out using online testing systems at eolymp.com and codeforces.com.

The task for knowledge control, which will indicate good mastery of the topic "Arrays" and a number of previous topics and, accordingly, indicate the possibility of moving to the next level, may be as follows: display elements of a given array in the following order: first minimal, then maximal, then the next minimal, then the next maximal etc.

Table 2 Topics and tasks covered by the medium level

The transition to the second level is

also accompanied by the active

participation of students in various

competitions and Olympiads.

Undoubtedly, the main skills that develop

in competitions are programming itself and the ability to look for errors in written programs. There are different formats for holding Olympiads and evaluating solutions. But for each of them, the number of points obtained for the proposed solution directly depends on its correctness. Therefore, it is necessary to implement the idea without errors, preferably from the first time. Otherwise, the participant must quickly identify and correct inaccuracies.

The ability to debug programs quickly is one of the most important skills in programming. Undoubtedly, the winners of prestigious programming Olympiads are very talented and persistent people. There are many competitions held by the largest IT companies. Technical recruiters have been monitoring the results of various competitions and specific participants for many years. The most promising and successful are offered an internship, combining it with university studies, with the opportunity to get a full- fledged job after graduation. In general, participation in programming Olympiads consists of two stages: creating effective algorithms for tasks and their implementation.

At first glance, it may seem that to achieve significant results in the Olympiads, it is enough to study a number of existing algorithms, and then only successfully use them during the competition, leaving others no chance of winning. In fact, it doesn't work that way. Otherwise it would not be so interesting to be engaged in Olympiad informatics. Tasks are formed in such a way that it is not enough to guess the algorithm that needs to be used to solve them. Almost always for a complete solution it is necessary to upgrade a known algorithm, supplement it, combine several algorithms in one program. One can't do without inventing own new ideas.

The task for knowledge control, which will indicate good mastery of the topic "Dynamic programming" for the second level may be the following task [9, task 5101]. Hodja Nasreddin is in the upper left cell of the n Ч n table, and his donkey is in the lower right. Hodja walks only to the right or down, the donkey walks only to the left or up. In how many ways can they meet in one cell? (The two methods are considered different if they have different routes of Hodge or donkey). One number n (1 ? n ? 50) is given at the input. Print one number - the number of ways Hodja and Donkey will meet. Since this number can be very large, print it modulo 9929.

To solve this problem it is necessary to know the Bellman optimality principle with a fairly simple filling of a two- dimensional array.

Table 3 Topics and tasks covered by the high level

The task for knowledge control, which will indicate good mastery of the above topic "Dynamic programming", but at the third level, may be the following task [9, task 1528]. A subsequence is formed from a string by removing zero or more characters from it. For the given three lines, you should count the number of their different non-empty common subsequences. Each test consists of three words in three different lines. The length of each word is slightly more than 50. Each word consists of lowercase Latin letters ('a'

- 'z'). Print the number of different non- empty common subsequences in a separate line for each test. To solve this problem, we need to use a three-dimensional array, the values of which will be filled using the Bellman principle of optimality.

The topic "Isomorphic representation of problems in computer science" is the author's and part of it was developed jointly with Bohdan Zadorozhny, who in 2019 won first place in the final stage of the competition for the defense of research works of the Small Academy of Sciences.

Table 4 Topics and tasks covered by the advanced level

Note that the topic "Approaches to reducing the time of programs that are associated with sequences and matrices" is well exposed in [10]. Quite a lot of information on the topics of the fourth level is given in [11-14].

Conclusions and research perspectives. The proposed four-level methodological system of training students for the Olympiads in informatics was successfully used in teaching students of Uzhgorod specialized boarding school with in-depth study of certain subjects (UzhSBSwiDSCS), at summer and winter students' programming schools in Kremenchug and summer programming schools in Khust. Many students of UzhSBSwiDSCS studied by this system of training, participated in Olympiads and became winners of various stages of the All-Ukrainian Student Olympiad in Informatics. This approach also has been successfully tested in distance learning [15]. Many of the students continued to participate in programming Olympiads as students of higher educational institutions. Over time, they received invitations and internships in the world's leading IT companies [16, 17].

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17. Yak uzhgorodski ajtivci Yevropu pidkoryuyut - As Uzhhhorod's IT spesialists conquer Europe.

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