Count number of even and odd numbers from input

Question

I had to write a program that accepted five numbers from the user. Then it will display the number of odd and even numbers, and a total sum of all numbers.

#include <iostream>
using namespace std;

int main()
{
    int a;
    int b;
    int c;
    int d;
    int e;
    int sum;
    int remainder;
    int bremainder;
    int cremainder;
    int dremainder;
    int eremainder;
    int even;
    int odd;
    int total = 0;
    int Ototal = 0;

    cout << "Please enter the 5 numbers you would like calculated: \n";
    cin >> a;
    cin >> b;
    cin >> c;
    cin >> d;
    cin >> e;

    remainder = a % 2;
    bremainder = b % 2;
    cremainder = c % 2;
    dremainder = d % 2;
    eremainder = e % 2;

    sum = (a + b + c + d + e);

    if (remainder = 0)
    {
        total+=remainder;
    }
    else {
        Ototal += remainder;
    }
    if (bremainder = 0)
    {
        total += bremainder;
    }
    else {
        Ototal += bremainder;
    }
    if (cremainder = 0)
    {
        total += cremainder;
    }
    else {
        Ototal += cremainder;
    }
    if (dremainder = 0)
    {
        total += dremainder;
    }
    else {
        Ototal += dremainder;
    }
    if (eremainder = 0)
    {
        total += eremainder;
    }
    else {
        Ototal += eremainder;
    }

    cout << total << "\n";

    cout << Ototal << "\n";

    cout << sum << "\n";
    system("PAUSE");
        return 0;
}

Answer 1

1. Do not use system("pause"). Read this
2. Stop using using namespace std. Read this
3. You have an unneccessary amount of variables. You don't need to have a variable to hold the remainder for each number.
4. Just have a function that determines whether the input number is odd or even. I think you might have to rethink the logic of your program.

//Your function should do the following:
//MAX is a const int. In your case it is 5
    for(int i=0; i<MAX; i++){
        if(numbers[i] % 2 == 0)
            evenNumbers++;
        else
            oddNumbers++;

        sum += numbers[i];
    }

Here is how I would have done it:

#include <iostream>
#include <vector>
#include <iterator>

using std::cin;
using std::cout;
using std::endl;
using std::vector;



int main(){

    int value = 0;
    int oddNumbers(0), evenNumbers(0), sum(0);


    std::istream_iterator<int> begin(cin);
    std::istream_iterator<int> end;


    //while(cin >> value)
    //  numbers.push_back(value);

    //Instead of a while loop, I use input stream iterators.
    vector<int> numbers;
    std::back_insert_iterator<std::vector<int>> iter (numbers);

    std::copy(begin,end,iter);


    //Range based for-loop (C++11)
    for(auto i : numbers){
        if(i % 2 == 0){
            evenNumbers++;
        }else {
            oddNumbers++;
        }

        sum += i;

    }

    cout << "# of odd numbers: " << oddNumbers << "\n";
    cout << "# of even numbers: " << evenNumbers << "\n";
    cout << "Sum of all numbers: " << sum << endl;



}

Answer 2

Inspired by @EngieOPs answer, I ended up with the following:

• I use std::copy_n instead of std::copy to read the values, because it was asking for a fixed sized input.
• I templated everything to enable counting of other types than int.
• I created a functor is_even for better readability.
• I use std::count_if and accumulate from the STL to calculate the end results.
• Instead of counting the odd numbers, I just use the difference between the number of inputs and the number of even variables.

I think the usage of std::count_if and std::accumulate is much more readable than a for loop. Whether a template makes sense would depend on the actual usage.

#include <iostream>
#include <vector>
#include <iterator>
#include <algorithm>
#include <numeric>

struct is_even
{
    template <class T>
    bool operator() (T value)
    {
        return (value % 2) == 0;
    }
};

template<class T>
void processInput(std::size_t count)
{
    std::istream_iterator<T> begin(std::cin);

    std::vector<T> numbers;
    std::back_insert_iterator<std::vector<T>> iter(numbers);
    std::copy_n(begin, count, iter);

    auto evenNumbers = std::count_if(numbers.begin(), numbers.end(), is_even());
    auto oddNumbers = numbers.size() - evenNumbers;
    auto sum = std::accumulate(numbers.begin(), numbers.end(), T());

    std::cout << "# of odd numbers: " << oddNumbers << "\n";
    std::cout << "# of even numbers: " << evenNumbers << "\n";
    std::cout << "Sum of all numbers: " << sum << std::endl;
}

int main(void)
{
    processInput<int>(5);

    return 0;
}