Assignment 2 Arrays and Functions

Transcription

1 Assignment 2 Arrays and Functions Assigned TA: Yohai Mandabi. Publication date: Introduction The geographic coordinate system is a grid allowing the specification of any location on Earth. The exact location of each place is represented by two angles, one for latitude and the other for longitude. The latitude represents the location on the north-south axis, where 0 is the Equator, 90 N is the North Pole and 90 S is the South Pole. The longitude represents the location on the west-east axis, and ranges between 180 W to 180 E, where 0 is the vertical line passing through the Royal Observatory, Greenwich, England. The angles are set in the center of the earth, and together represent a straight line, which represents a location on the surface of the earth (Figure 1). According to the geographic coordinate system, the exact location of Be'er Sheva is N E. The first part represents the Figure 1 - Latitude and Longitude angles. φ Latitude angle. λ Longitude angle. From wikipedia.org latitude and the latter the longitude. Note that the latitude is comprised as DD MM'SS"C while the longitude is comprised as DDD MM'SS"C where: D Degrees. M Minutes. S Seconds. C Cardinal Direction. Due to ASCII limitations, coordinates should be written in the following format DD*MM'SS"C DDD*MM'SS"C the * char should be used instead of the char.

2 Guidelines 1. Please read this document carefully, before starting to work on this assignment. 2. You are not allowed to use any material which was not covered in class so far. 3. You are allowed to use the libraries stdio.h, string.h and math.h. 4. It is not allowed to change function headers given to implement. 5. You can and encouraged to implement helper functions. Your code will be much shorter this way. 6. The output of your program should be exactly the same as the output of the example program published with this assignment. Before writing the code for each section, spend a few minutes to enter some input in the example program and get the idea of how the function should behave. 7. The maximum input length is 99; you should not check longer inputs. 8. Input errors should be dealt with only in the main menu (choosing 1-7). You can assume that the rest of the input is written in the right format. 9. You should define the following constants in your code: NUMBER_OF_FIELDS 2, MAX_NUMBER_OF_CITIES 20, MAX_SIZE 100, PI While DD MM'SS"C DDD MM'SS"C is the longest template for a set of coordinates, it is possible to have a shorter set of coordinates for single digit angle locations. For example the location of London is represented by the coordinates 51 30'26"N 0 7'39"W where the longitude angle is represented by the template D M'SS"C. Your program should be able to deal with this kind of input as well.

3 Functions int addcity(char table[][number_of_fields][max_size],int numberofcities,char cityname[],char coordinates[]); The function gets table, an array defined according to Figure 2. Figure 2 - Properties of the array 'table'. Each cell in the array holds an array sized NUMBER_OF_FIELDS (2), where the first index holds a string containing a city name, and the other the coordinates of that city. numberofcities, an integer containing the current amount of cities saved in the array table. cityname, a string containing a city name that should be saved in the array table. coordinate, a string containing the coordinates of the city that should be saved in the array table. The function saves the data in cityname and coordinate in the next available cell of the array table (e.g. if table contains data of 5 cities, the data for the 6 th city should be saved at cell no.5). The function returns 1 upon adding a city to the array successfully, otherwise the function returns 0. In order to add the city of Jerusalem to the database, you should complete the following steps: There are no input and output commands in this function, i\o is done from the main function. In case the function could not add the new location to the database, a message is printed "Could not add the city of <city name> to the database".

4 int removecity(char table[][number_of_fields][max_size],int numberofcities,char cityname[]); The function gets table, an array containing data for the location of numberofcities amount of cities. The function removes the city, with the same city name stored in cityname, from the array table. The function returns 1 upon successful removal of the city data from the array table, in case the city doesn't exist in the array, the function returns 0. You can assume there are no two cities with the same name in the array. For Example: In order to remove the city of Jerusalem from the database you should complete the following steps: There are no input and output commands in this function, i\o is done from the main function. In case the function could not remove a location from the database, a message is printed "Could not find <city name> in the database".

5 double distance(char coordinates1[], char coordinates2[]); The function gets two strings; coordinate1 and coordinate2, representing coordinates of two cities. The function returns the distance between those two cities using Equation 1. distance = arccos( sin(φ 1 ).sin(φ 2 ) + cos(φ 1 ).cos(φ 2 ).cos(δλ) ).R Equation 1 - Distance between two coordinates φ 1 latitude angle of coordinate 1. φ 2 latitude angle of coordinate 2. Δλ The delta between the two longitude angles. R The earth radius in km (6371). All of the trigonometric functions are part of the library math.h, the function for arccos appears under the name acos. The trigonometric library functions accept angles in radians. In order to get the right results, the angles representing South and West should be defined as negative angles. For example: In order to calculate the distance between Jerusalem and London. There are no input and output commands in this function, i\o is done from the main function. You can assume the two cities exist in the database.

6 void printcitiescoordinates(char table[][number_of_fields][max_size],int numberofcities); The function gets table, an array containing data of cities' coordinates and numberofcities the amount of cities in the array. The function prints the data stored in the array on screen. The cities appear in the table in the same order as they are stored in the array. Please note that each table printed is numbered (marked). For Example: void sortcitiesntos(char table[][number_of_fields][max_size],int numberofcities); The function gets table, an array containing data of cities' coordinates and numberofcities the amount of cities in the array. The function sorts the array according to the coordinates of the cities from North to South. The table is sorted as follows.

7 void citiesnearby(char table[][number_of_fields][max_size],int numberofcities, char coordinates[],double radius); The function gets table, an array containing data of each city's coordinates, numberofcities the amount of cities in the array, coordinate, a location on earth and radius, a number representing distance from the coordinate. The function prints on screen all of the cities stored in the array table in distance radius or less from the given coordinate, according to the distance from the coordinate (closest to farthest). For example: When searching for cities stored in the database, in distance 5000km from the coordinates of Athens.