Question

In C++. Define a class Country that stores the name of the country, its population, and its area. Store the country name as a C-string. Write a main function that initializes an array with at least 5 objects of this class and sorts and prints this array in three different ways:

• By population
• By population density (people per square kilometer)

Do not ask the user to enter country data. Use qsort to sort the array.

• Also sort alphabetically by country name, ignoring the case (upper-case or lower-case)

Also: Separately program for below;

a) Add to the class Country a method saveInFile, which gets a file object as an explicit argument and saves the Country object used as an implicit argument at the end of the corresponding file.

b) Add to the class Country a class-level method readFromFile, which will take a file object and an integer position as explicit arguments and will return a Country object with data read from the Country stored at position position in the corresponding file.

Answer 1

PROGRAM CODE (1)

#include <iostream>
#include <string.h>
using namespace std;

// Country class

class Country {
  
   public:
  
       // All required attributes  
      
       char *name;
       double population;
       double area;
};

// A comparator function to sort countries in ascending order according to their names

int name(const void *a, const void *b) {
  
   Country *l = (Country*)a;
   Country *r = (Country*)b;
  
   return strcmp(l->name, r->name);
}

// A comparator function to sort countries in ascending order according to their population

int pop(const void *a, const void *b) {
  
   double l = ((Country*)a)->population;
   double r = ((Country*)b)->population;
  
   return l-r;
}

// A comparator function to sort countries in ascending order according to their area

int area(const void *a, const void *b) {
  
   double l = ((Country*)a)->area;
   double r = ((Country*)b)->area;
  
   return l-r;
}

// A function to print countries

void print(Country countries[], int size) {
  
   cout << "Name\tPopulation\tArea" << endl;
  
   for(int i=0; i<size; i++) {
      
       cout << countries[i].name << "\t" << countries[i].population << " billion \t" << countries[i].area << endl;
   }
   cout << endl;
}

int main() {
  
   // Initialzing an array of 5 Country objects
  
   Country countries[] = {{"China", 13.1, 630000}, {"US", 20.0, 700000}, {"UK", 11.1, 500000},
   {"India", 18, 880000}, {"Russia", 15, 700000}};
  
   // Printing all information in 3 different ways
  
   // First of all sorting by names using qsort
   qsort((void*)countries, 5, sizeof(countries[0]), name);
  
   cout << "*** Countries according to their Names(Sorted) ***\n" << endl;
   print(countries, 5);   // Printing by calling print function
  
   // First of all sorting by population using qsort  
   qsort((void*)countries, 5, sizeof(countries[0]), pop);
  
   cout << "*** Countries according to their Population(Sorted) ***\n" << endl;
   print(countries, 5);   // Printing by calling print function
  
  
   // First of all sorting by area using qsort
   qsort((void*)countries, 5, sizeof(countries[0]), area);
  
   cout << "*** Countries according to their Area(Sorted) ***\n" << endl;
   print(countries, 5);   // Printing by calling print function
  
   return 0;
}

SAMPLE OUTPUT1

dede Name Area C:\Users\Dell OneDrive\Desktop\CPP July 2020\Country.exe *** Countries according to their Names (Sorted) Population Area China 13.1 billion 630000 India 18 billion 880000 Russia 15 billion 700000 UK 11.1 billion 500000 US 20 billion 700000 *** Countries according to their population (Sorted) *** Name Population 11.1 billion 500000 China 13.1 billion 630000 Russia 15 billion 700000 India 18 billion 880000 US 20 billion 700000 *** Countries according to their Area(Sorted) *** Name Population Area 11.1 billion 500000 China 13.1 billion 630000 US 20 billion 700000 Russia 15 billion 700000 India 18 billion 880000 UK UK Process exited after 0.8143 seconds with return value o Press any key to continue .

SEPARATE PROGRAM CODE FOR PART a and b

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;

// Country class

class Country {
  
   public:
  
       // All required attributes  
      
       char *name;
       double population;
       double area;
      
       // Adding All Required methods
      
       void saveInFile(ofstream &w) {
          
           // Saving that country object in that file
          
           w << this->name << " " << this->population << " " << this->area << endl;
       }
      
       Country readFromFile(ifstream &r, int position){
          
           Country c;
          
           // Reading from file until that position comes
          
           int count = 0;
          
           while(true) {
              
               count ++;
              
               char* name;
               double p, a;
              
               r >> name >> p >> a;

// Reading until that position in the file
                          
               if(position == count) {
                  
                   c.name = name;
                   c.population = p;
                   c.area = a;
                   break;
               }
                     
           }
          
           // Finally return that object
          
           return c;
       }
};

int main() {
  
   // A Test program to check both functions
  
   Country c1; c1.name = "US"; c1.population = 10; c1.area = 100000;
   Country c2; c2.name = "India"; c2.population = 20; c2.area = 150000;
   Country c3; c3.name = "Australia"; c3.population = 25; c3.area = 200000;
  
   // Saving all objects in file countries.txt
  
   ofstream w("countries.txt", ios::app);
//  
//   c1.saveInFile(w);
//   c2.saveInFile(w);
//   c3.saveInFile(w);
  
   w.close();
  
   // Now reading object at 2nd position in file countries.txt
  
   ifstream r("countries.txt");
  
   Country c = c1.readFromFile(r, 2);
  
   cout << "The country at position 2" << endl;
  
   cout << "Name: " << c.name << endl
   << "Population: " << c.population << endl
   << "Area: " << c.area << endl;  
   return 0;
}

countries.txt

countries.txt - Notepad File Edit Format View Help JUS 10 100000 India 20 150000 Australia 25 200000

SAMPLE OUTPUT2

C:\Users\Dell OneDrive\Desktop\CPP July 2020 Country.exe The country at position 2 Name: India Population: 20 Area: 150000 Process exited after 0.3449 seconds with return value o Press any key to continue .

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