Question

What's wrong with my code? :

I'm trying to use recursive functions to display and count all the even numbers of an array. However, I can't seem get the program output the number of even integers .

Here's the output I want:

Here are the 5 even numbers: // Luckily, however, my code does output all the even numbers. But, I also want the program to tell me how may even integers there are.
2 8 14 18 22

MY CODE IS AT THE VERY BOTTOM OF THE PAGE

Here are the complete instructions to give you an Idea of what we're up against....

Write a program that uses a recursive function to find all even numbers in an array.

1.) Declare an array named  values
- Size = 10
- Initialize the array with values like these: 2, 5, 7 ,8, 11, 14, 17, 18, 22, 23

2.) In main(), call a function named  showEvens
- The function is a recursive, void-returning function.
- The array, as well as one or two other parameters is passed to the function.
- The function begins by checking the first array value (at index 0) to see if it’s
an even number.
o When the program is finished, only even numbers are displayed. (see
output)

- Each time the function is called (recursively), one array value is checked to see if it
is even.
o If an even number is encountered, a count variable is incremented. The
count variable keeps track of the number of even numbers in the array.

3.) Remember, that a recursive function must have a base case that stops the recursion.
- So after all array values have been checked, the recursion stops.

4.) In the end, the number of even numbers is display, along with the numbers.

/* OUTPUT
Here are the 5 even numbers:
2 8 14 18 22

MY CODE:

Overall, the program won't allow me to increment the amount of even integers. That's the problem I have.

# include <iostream>
# include <cstring>
# include <string>
using namespace std;

void showEvens(int values[], int index);

int main()
{

   int values[10] = { 2,5,7,8,11,14,17,18,22,23 };
   int evenCounter; // The variable used to count the number of even integers
   int index;

   index = 0;
evenCounter = 0;

   showEvens(values, index);
   cout << endl;

   cout << evenCounter; // I wan't this output "5". However, the program won't allow me.
  
  
   cout << endl;
   system("pause");
   return 0;
}

void showEvens(int values[], int index)
{
   int evenCounter;

   if (index == 10) // Base Case -- The Function is exited when the index is 10
   {

       return;

   }
  
   if ((values[index] % 2) == 0) // Determines whether or not an element array is even
   {

       cout << values[index] << '\t';
evenCounter++; // Including this part will result in an error.  I don't understand why . It won't allow me to increment.
      
   }
  
   showEvens(values, index + 1); // The index gets incremented every time the function is called

}

Answer 1

C++ Program:

# include <iostream>
# include <cstring>
# include <string>

using namespace std;

/* Update function prototype so that variable evenCounter is passed as reference variable */
void showEvens(int values[], int index, int &evenCounter);

int main()
{

int values[10] = { 2,5,7,8,11,14,17,18,22,23 };
int evenCounter; // The variable used to count the number of even integers
int index;
index = 0;
evenCounter = 0;

/* Pass variable eventCounter as reference variable */
showEvens(values, index, evenCounter);

cout << endl;

cout << evenCounter; // I wan't this output "5". However, the program won't allow me.

cout << endl;
system("pause");

return 0;
}

/* Update with one more variable of reference type */
void showEvens(int values[], int index, int &evenCounter)
{
if (index == 10) // Base Case -- The Function is exited when the index is 10
{
return;
}

if ((values[index] % 2) == 0) // Determines whether or not an element array is even
{
cout << values[index] << '\t';
evenCounter++; // Including this part will result in an error. I don't understand why . It won't allow me to increment.
}

/* Change function call by including extra variable */
showEvens(values, index + 1, evenCounter); // The index gets incremented every time the function is called
}

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Sample Run: