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  1. //Amari Mosley CSC5 Chapter 6, P. 373, #15
  2. //
  3. /*****************************************************************
  4.  *
  5.  * Population Calculation
  6.  * _______________________________________________________________
  7.  * This program displays the size of a population for any number
  8.  * of years, based on a starting size, birth rate, and death rate.
  9.  *
  10.  * Computation is based on the formula:
  11.  *   N = P + (B * P) - (D * P)
  12.  *   where N = new population, P = previous population,
  13.  *         B = birth rate, D = death rate
  14.  * _______________________________________________________________
  15.  * INPUT
  16.  *   startSize : starting population size 
  17.  *   birthRate : annual birth rate as a percentage 
  18.  *   deathRate : annual death rate as a percentage 
  19.  *   years     : number of years to display 
  20.  *
  21.  * OUTPUT
  22.  *   The population size for each year
  23.  *
  24.  *****************************************************************/
  25. #include <iostream>
  26. #include <iomanip>
  27. using namespace std;
  28.  
  29. // Function prototype
  30. double calcPopulation(double prevPop, double birthRate, double deathRate);
  31.  
  32. int main()
  33. {
  34.     double startSize;   // starting population size
  35.     double birthRate;   // annual birth rate 
  36.     double deathRate;   // annual death rate 
  37.     int years;          // number of years to display
  38.     double population;  // population size for the current year
  39.  
  40.     // Get starting size with input validation
  41.     cout << "Enter the starting size of the population: ";
  42.     cin >> startSize;
  43.     while (startSize < 2)
  44.     {
  45.         cout << "Starting size must be at least 2. Please re-enter: ";
  46.         cin >> startSize;
  47.     }
  48.  
  49.     // Get birth rate with input validation
  50.     cout << "Enter the annual birth rate (as a percentage): ";
  51.     cin >> birthRate;
  52.     while (birthRate < 0)
  53.     {
  54.         cout << "Birth rate cannot be negative. Please re-enter: ";
  55.         cin >> birthRate;
  56.     }
  57.  
  58.     // Get death rate with input validation
  59.     cout << "Enter the annual death rate (as a percentage): ";
  60.     cin >> deathRate;
  61.     while (deathRate < 0)
  62.     {
  63.         cout << "Death rate cannot be negative. Please re-enter: ";
  64.         cin >> deathRate;
  65.     }
  66.  
  67.     // Get number of years with input validation
  68.     cout << "Enter the number of years to display: ";
  69.     cin >> years;
  70.     while (years < 1)
  71.     {
  72.         cout << "Number of years must be at least 1. Please re-enter: ";
  73.         cin >> years;
  74.     }
  75.  
  76.     // Convert percentages to decimals
  77.     birthRate = birthRate / 100;
  78.     deathRate = deathRate / 100;
  79.  
  80.     // Display the population for each year
  81.     cout << fixed << setprecision(2);
  82.     cout << "\nYear\tPopulation" << endl;
  83.     cout << "-----------------------" << endl;
  84.  
  85.     population = startSize;
  86.     for (int year = 1; year <= years; year++)
  87.     {
  88.         population = calcPopulation(population, birthRate, deathRate);
  89.         cout << year << "\t" << population << endl;
  90.     }
  91.  
  92.     return 0;
  93. }
  94.  
  95.  
  96.  // calcPopulation
  97.  //   Receives the previous population size, birth rate, and death
  98.  //   rate (as decimals) and returns the new population size.
  99.  //   Formula: N = P + BP - DP
  100.  
  101. double calcPopulation(double prevPop, double birthRate, double deathRate)
  102. {
  103.     return prevPop + (birthRate * prevPop) - (deathRate * prevPop);
  104. }
Success #stdin #stdout 0s 5292KB
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stdin
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1000
3
1
3
stdout
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Enter the starting size of the population: Enter the annual birth rate (as a percentage): Enter the annual death rate (as a percentage): Enter the number of years to display: 
Year	Population
-----------------------
1	1020.00
2	1040.40
3	1061.21
https://ideone.com/oiyGU9
CH 6. #15
language:
C++ (gcc 8.3)
created:
7 days ago
visibility:
public

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