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  1.  
  2.  //Dione Torrevillas          CS1A          Chapter 6, P. 373, #15
  3.  //
  4.  /****************************************************************
  5.   *
  6.   * CALCULATE POPULATION GROWTH
  7.   *_______________________________________________________________
  8.   * This program computes the population size over a number of
  9.   * years based on the starting population, annual birth rate,
  10.   * and annual death rate. A function calculates the population
  11.   * for each year.
  12.   *
  13.   * Computation is based on the formula:
  14.   * New Population = Previous Population +
  15.   * (Birth Rate * Previous Population) -
  16.   * (Death Rate * Previous Population)
  17.   *_______________________________________________________________
  18.   * INPUT
  19.   *   population     : Starting population size
  20.   *   birthRate      : Annual birth rate percentage
  21.   *   deathRate      : Annual death rate percentage
  22.   *   years          : Number of years to display
  23.   *
  24.   * OUTPUT
  25.   *   population     : Population size for each year
  26.   *
  27.   ****************************************************************/
  28.  
  29. #include <iostream>
  30. #include <iomanip>
  31. using namespace std;
  32.  
  33. // Function prototype
  34. double calculatePopulation(double, double, double);
  35.  
  36. int main()
  37. {
  38.     double population;   //INPUT - Starting population
  39.     double birthRate;    //INPUT - Annual birth rate
  40.     double deathRate;    //INPUT - Annual death rate
  41.     int years;           //INPUT - Number of years
  42.     int year;            //OUTPUT - Year being displayed
  43.  
  44.     // Get the starting population
  45.     cout << "Enter the starting population: ";
  46.     cin >> population;
  47.  
  48.     // Validate the starting population
  49.     while (population < 2)
  50.     {
  51.         cout << "Enter a population of at least 2: ";
  52.         cin >> population;
  53.     }
  54.  
  55.     // Get the annual birth rate
  56.     cout << "Enter the annual birth rate (%): ";
  57.     cin >> birthRate;
  58.  
  59.     // Validate the birth rate
  60.     while (birthRate < 0)
  61.     {
  62.         cout << "Enter a nonnegative birth rate: ";
  63.         cin >> birthRate;
  64.     }
  65.  
  66.     // Get the annual death rate
  67.     cout << "Enter the annual death rate (%): ";
  68.     cin >> deathRate;
  69.  
  70.     // Validate the death rate
  71.     while (deathRate < 0)
  72.     {
  73.         cout << "Enter a nonnegative death rate: ";
  74.         cin >> deathRate;
  75.     }
  76.  
  77.     // Get the number of years
  78.     cout << "Enter the number of years: ";
  79.     cin >> years;
  80.  
  81.     // Validate the number of years
  82.     while (years < 1)
  83.     {
  84.         cout << "Enter at least 1 year: ";
  85.         cin >> years;
  86.     }
  87.  
  88.     // Convert percentages to decimal values
  89.     birthRate = birthRate / 100;
  90.     deathRate = deathRate / 100;
  91.  
  92.     // Display the table heading
  93.     cout << endl;
  94.     cout << "Year       Population" << endl;
  95.     cout << "---------------------" << endl;
  96.  
  97.     // Calculate and display population for each year
  98.     for (year = 1; year <= years; year++)
  99.     {
  100.         // Call function to calculate new population
  101.         population = calculatePopulation(population,
  102.                                           birthRate,
  103.                                           deathRate);
  104.  
  105.         // Display the population for the year
  106.         cout << setw(4) << year
  107.              << setw(17) << fixed << setprecision(0)
  108.              << population << endl;
  109.     }
  110.  
  111.     return 0;
  112. }
  113.  
  114. // Function definition
  115. // Calculates and returns the new population
  116. double calculatePopulation(double population,
  117.                            double birthRate,
  118.                            double deathRate)
  119. {
  120.     double newPopulation;   // New population size
  121.  
  122.     // Calculate the population for one year
  123.     newPopulation = population +
  124.                     (birthRate * population) -
  125.                     (deathRate * population);
  126.  
  127.     return newPopulation;
  128. }
  129.  
Success #stdin #stdout 0.01s 5292KB
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stdin
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1000
5
2
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stdout
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Enter the starting population: Enter the annual birth rate (%): Enter the annual death rate (%): Enter the number of years: 
Year       Population
---------------------
   1             1030
   2             1061
   3             1093
   4             1126
   5             1159
https://ideone.com/0pkWtz
language:
C++ (gcc 8.3)
created:
22 hours ago
visibility:
public

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