Arrays. Independent Part. Contents. Programming with Java Module 3. 1 Bowling Introduction Task Intermediate steps...

Transcription

1 Programming with Java Module 3 Arrays Independent Part Contents 1 Bowling Introduction Task Intermediate steps Extension Tic Tac Toe Introduction Task Intermediate steps Extensions Search and sort algorithms Introduction Preparations Search algorithms Task Extensions Sort algorithms Introduction Task Extension

2 Keywords Data structure Array Array Index Array Element Array Dimension Array Length Array Iteration Two-dimensional Array Authors: Lukas Fässler, Barbara Scheuner Date: 18 July 2018 Version: 1.1 Hash: d2eb005 The authors try the best to provide an error free work, however there still might be some errors. The Authors are thankful for your feedback and suggestions. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. To view a copy of this license, visit 2

3 1 Bowling 1.1 Introduction In bowling, the results are typically noted and evaluated in a table. The number of pins knocked over is noted in each round. Therefore, numbers between 0 (no pin is knocked down) and 10 (all pins are knocked down - a so-called Stricke) are possible. Players Runde Runde Runde Runde Runde Summe Table 1: Results of a bowling game. 1.2 Task Your program should be able to store and evaluate the results of 3 players during 5 rounds (see table 1). Use a two-dimensional array for storing the results and a one-dimensional array for calculating the sum. 1.3 Intermediate steps Proceed as follows: Declartion of the variables: Declare a variable results as a two-dimensional Integer array (3 players, 5 rounds) and sumas a one-dimensional Integer. Reading results: Read the result into the array results. It should be possible to enter the points for each of the 5 rounds and for each of the 3 players. Calculation of the results: Store the sum of the points of each player in the array sum. 3

4 Output of the results: Output the point table (results) and the sum (sum) on the screen in tabular form. 1.4 Extension Check whether the entered number is allowed. Output at end of the game how many strikes have been thrown and how often no pin has been knocked down by each player. Adapt your program so that the number of rounds and the number of players can be entered. Output the winner of the game. Calculate in which round each player has made his first strike and output the result on the screen. 2 Tic Tac Toe 2.1 Introduction Tic Tac Toe (also known as noughts and crosses or Xs and Os) is a game for two players who take turns marking (e.g. with x or o) the empty spaces. The player who succeeds in marking all spaces of a column, a row or a diagonal wins the game. 2.2 Task Two persons play alternately. With each turn, it must be made clear which players turn it is. The current board shall be output after each turn. It shall be displayed if a person has won. 2.3 Intermediate steps Play the game on a paper first. Which steps are performed in succession? Program the following three steps: Define a 3 3-board of type Character. Introduce a variable player, which can take two values (e.g. 1 and 2). Set all values of the board to spaces (' '). Program the output of the board. 4

5 : 2: 3: Player 1: Enable the player to enter the field which he want to mark via a user input. Set the corresponding character (e.g x or o) in the fields desired by the player. Repeat the turns until the board is completely marked or someone has won. 2.4 Extensions Check whether a desired field is already marked before executing the move. If the field is already marked, the player shall make another input. The same shall happen if the player chooses a field that is outside of the board. 3 Search and sort algorithms 3.1 Introduction Searching in collected data and sorting data are two of the most common tasks a programmer is faced with. There are numerous books on these topics and since search and sort algorithms are used so often, it is particularly important that they are programmed as efficiently as possible. Furthermore, there is a large number of strategies which can be applied to implement a sort algorithm. A lot of effort was made to develop the design and analysis of these algorithms since the middle of the 20th century. Here, we will only get to know a small selection Preparations Download the initial program lotterynumbers.py onto your computer. Familiarize yourself with the program. 3.2 Search algorithms As mentioned above, there are several search algorithms that differ in their structure and their efficiency. The most famous are the linear search and the binary search. We only want to consider the linear search. 5

6 How does the linear search work? A set of elements (e.g. an array) is searched according to a certain element. The search begins at the first element and the elements are passed through in the order in which they were stored. If the element considered corresponds to the sought element, the search is terminated, otherwise the search is continued Task Search the array for the maximum value and output the value and the position of the data in the console. How can we search for the maximum value? The position of the (current) maximum is stored in the variable max. Initially, the first element of the array is taken as the maximum. Now, all elements of the array (except the first one) are run. If the value of an element at the current position is larger than the current maximum, then this position is stored in max. 3.3 Extensions Search the minimum of the array in the same way. Use a common loop for both search. Consider what happens if the sought value occurs more than once. How does your program react to that? How do you assess the searching effort? How could it be optimized? 3.4 Sort algorithms Introduction The goal of sort algorithms is to sort the elements of a set according to a certain criterion. After sorting, the elements are available in ascending or descending order. There are several sort algorithms which differ in their structure and their efficiency. The most famous are Bubble sort, Insertion sort, Merge sort and Quick sort. 6

7 How does Bubble sort work (for a ascending order see figure??)? 1. Two neighboring elements are compared. The comparison begins with the elements with the index 0 and 1, then 1 and 2, then 2 and 3, etc. 2. If the value of the left element is larger than the value of the right one, the two elements are swapped. 3. In one array run, the largest element moves to the end of the array. 4. Now, the steps 1 to 3 are repeated to move the second-largest element at the penultimate position. Note: The comparison of the second-largest and the largest element is omitted since it was already sorted. 5. The steps 1 to 4 are repeated until the two smallest elements are compared Task Try to implement Bubble-Sort-algorithm! Extension How could the efficiency of Bubble sort be improved? 7

8 Figure 1: Bubble-Sort. Details siehe Text. 8