Question

Can someone make this code work without using template?

C++

using namespace std;

template < typename T>

   void print_array(T arr[], int size)
   {

       ofstream outfile;

       outfile.open("/Users/android/Desktop/outfile.txt");

       cout << "Printing Array: " << endl;

       for (int i = 0; i < size; i++)
       {

           cout << arr[i] << endl;

           outfile << arr[i] << endl;
       }
   }

template < typename T>

   class MergeHelper
   {

       int size;

       public:

           MergeHelper(int size)
           {

               this->size = size;
           }

       void merge(T Arr[], int start, int mid, int end)
       {

           // create a temp array

           T temp[end - start + 1];

           // crawlers for both intervals and for temp

           int i = start, j = mid + 1, k = 0;

           // traverse both arrays and in each iteration add smaller of both elements in temp

           while (i <= mid && j <= end)
           {

               if ((Arr[i] < Arr[j]) || (Arr[i] == Arr[j]))
               {

                   temp[k] = Arr[i];

                   k += 1;
                   i += 1;
               }
               else
               {

                   temp[k] = Arr[j];

                   k += 1;
                   j += 1;
               }
           }

           // add elements left in the first interval

           while (i <= mid)
           {

               temp[k] = Arr[i];

               k += 1;
               i += 1;
           }

           // add elements left in the second interval

           while (j <= end)
           {

               temp[k] = Arr[j];

               k += 1;
               j += 1;
           }

           // copy temp to original interval

           for (i = start; i <= end; i += 1)
           {

               Arr[i] = temp[i - start];
           }
       }

       void mergeSort(T Arr[], int start, int end)
       {

           if (start < end)
           {

               int mid = (start + end) / 2;

               mergeSort(Arr, start, mid);

               mergeSort(Arr, mid + 1, end);

               merge(Arr, start, mid, end);
           }
       }
   };

// MAIN METHOD

int main()
{

   int num_elements = 0;

   cout << "Enter a sorting size for the array (between 1 and 16): ";

   while (!(cin >> num_elements) || num_elements > SORT_MAX_SIZE || num_elements < 1)
   {

       // Explain error

       cout << "Error: Enter a number between 1 and 16: ";

       // clear previous input

       cin.clear();

       // discard previous input

       cin.ignore(123, '\n');
   }

   // what type of data do you want to enter?

   cout << "What type of data do you want to enter? " << endl;

   cout << "1: Integer" << endl;

   cout << "2: String" << endl;

   cout << "3: Dollar" << endl;

   int choice;

   cin >> choice;

   int arr_int[num_elements];

   string arr_str[num_elements];

   Dollar arr_dollar[num_elements];

   // Array<string, SORT_MAX_SIZE> stringarray;

   // Array<Dollar, SORT_MAX_SIZE> dollararray;

   // Array<int, SORT_MAX_SIZE> intarray;

   switch (choice)
   {

       case 1:
           {

               for (int i = 0; i < num_elements; i++)
               {

                   cout << "Enter element #" << i + 1 << ": ";

                   cin >> arr_int[i];
               }

               MergeHelper<int> merger(num_elements);

               merger.mergeSort(arr_int, 0, num_elements - 1);

               print_array(arr_int, num_elements);

               break;
           }

       case 2:
           {

               for (int i = 0; i < num_elements; i++)
               {

                   cout << "Enter element #" << i + 1 << ": ";

                   cin >> arr_str[i];
               }

               MergeHelper<string> merger(num_elements);

               merger.mergeSort(arr_str, 0, num_elements - 1);

               print_array(arr_str, num_elements);

               break;
           }

       case 3:
           {

               for (int i = 0; i < num_elements; i++)
               {

                   cout << "Enter element #" << i + 1 << ": ";

                   cout << "Dollars: ";

                   int whole;
                   cin >> whole;

                   double part;
                   cin >> part;

                   Dollar *buffer = new Dollar(whole, part, "Dollar");

                   arr_dollar[i] = *buffer;
               }

               MergeHelper<Dollar> merger(num_elements);

               merger.mergeSort(arr_dollar, 0, num_elements - 1);

               print_array(arr_dollar, num_elements);

               break;
           }
   }

   return 0;

}

Answer 1

A template is a powerful tool that is used for generating generic code for any type of data type. Let's say we have a sort STL implemented in the library but while passing an array through it we don't specify its data type that it is float or an int or a string array. Then how the code decides to take which algorithm. So here comes the templates in C++ which are used for overcoming this problem. In your code, they have utilized the same code for each of the three cases of int, string, and dollar. So if you want to do the same without using the templates then we will have to write the function MergeHelper and print_array for each of the datatype separately.

#include <bits/stdc++.h>

using namespace std;

//for intergers
void print_array(int arr[], int size)
{
    ofstream outfile;
    outfile.open("/Users/android/Desktop/outfile.txt");
    cout << "Printing Array: " << endl;
    for (int i = 0; i < size; i++)
    {
        cout << arr[i] << endl;
        outfile << arr[i] << endl;
    }
}

void print_array(string arr[], int size)
{
    ofstream outfile;
    outfile.open("/Users/android/Desktop/outfile.txt");
    cout << "Printing Array: " << endl;
    for (int i = 0; i < size; i++)
    {
        cout << arr[i] << endl;
        outfile << arr[i] << endl;
    }
}
void print_array(Dollar arr[], int size)
{
    ofstream outfile;
    outfile.open("/Users/android/Desktop/outfile.txt");
    cout << "Printing Array: " << endl;
    for (int i = 0; i < size; i++)
    {
        cout << arr[i] << endl;
        outfile << arr[i] << endl;
    }
}

//mergeHelper function for each cases

//int case
class MergeHelper
{
    int size;

public:
    MergeHelper(int size)
    {
        this->size = size;
    }
    void merge(int Arr[], int start, int mid, int end)
    {

        // create a temp array
        int temp[end - start + 1];

        // crawlers for both intervals and for temp

        int i = start, j = mid + 1, k = 0;

        // traverse both arrays and in each iteration add smaller of both elements in temp

        while (i <= mid && j <= end)
        {

            if ((Arr[i] < Arr[j]) || (Arr[i] == Arr[j]))
            {

                temp[k] = Arr[i];

                k += 1;
                i += 1;
            }
            else
            {

                temp[k] = Arr[j];

                k += 1;
                j += 1;
            }
        }

        // add elements left in the first interval

        while (i <= mid)
        {
            temp[k] = Arr[i];
            k += 1;
            i += 1;
        }

        // add elements left in the second interval

        while (j <= end)
        {
            temp[k] = Arr[j];
            k += 1;
            j += 1;
        }

        // copy temp to original interval

        for (i = start; i <= end; i += 1)
        {
            Arr[i] = temp[i - start];
        }
    }

    void mergeSort(int Arr[], int start, int end)
    {

        if (start < end)
        {

            int mid = (start + end) / 2;

            mergeSort(Arr, start, mid);

            mergeSort(Arr, mid + 1, end);

            merge(Arr, start, mid, end);
        }
    }
};

//string case
class MergeHelper
{
    int size;

public:
    MergeHelper(int size)
    {
        this->size = size;
    }
    void merge(string Arr[], int start, int mid, int end)
    {

        // create a temp array
        string temp[end - start + 1];

        // crawlers for both intervals and for temp

        int i = start, j = mid + 1, k = 0;

        // traverse both arrays and in each iteration add smaller of both elements in temp

        while (i <= mid && j <= end)
        {

            if ((Arr[i] < Arr[j]) || (Arr[i] == Arr[j]))
            {

                temp[k] = Arr[i];

                k += 1;
                i += 1;
            }
            else
            {

                temp[k] = Arr[j];

                k += 1;
                j += 1;
            }
        }

        // add elements left in the first interval

        while (i <= mid)
        {

            temp[k] = Arr[i];

            k += 1;
            i += 1;
        }

        // add elements left in the second interval

        while (j <= end)
        {

            temp[k] = Arr[j];

            k += 1;
            j += 1;
        }

        // copy temp to original interval

        for (i = start; i <= end; i += 1)
        {

            Arr[i] = temp[i - start];
        }
    }

    void mergeSort(string Arr[], int start, int end)
    {

        if (start < end)
        {

            int mid = (start + end) / 2;

            mergeSort(Arr, start, mid);

            mergeSort(Arr, mid + 1, end);

            merge(Arr, start, mid, end);
        }
    }
};

//dollar case
class MergeHelper
{
    int size;

public:
    MergeHelper(int size)
    {
        this->size = size;
    }
    void merge(Doller Arr[], int start, int mid, int end)
    {

        // create a temp array
        Doller temp[end - start + 1];

        // crawlers for both intervals and for temp

        int i = start, j = mid + 1, k = 0;

        // traverse both arrays and in each iteration add smaller of both elements in temp

        while (i <= mid && j <= end)
        {

            if ((Arr[i] < Arr[j]) || (Arr[i] == Arr[j]))
            {

                temp[k] = Arr[i];

                k += 1;
                i += 1;
            }
            else
            {

                temp[k] = Arr[j];

                k += 1;
                j += 1;
            }
        }

        // add elements left in the first interval

        while (i <= mid)
        {

            temp[k] = Arr[i];

            k += 1;
            i += 1;
        }

        // add elements left in the second interval

        while (j <= end)
        {

            temp[k] = Arr[j];

            k += 1;
            j += 1;
        }

        // copy temp to original interval

        for (i = start; i <= end; i += 1)
        {

            Arr[i] = temp[i - start];
        }
    }

    void mergeSort(Doller Arr[], int start, int end)
    {

        if (start < end)
        {

            int mid = (start + end) / 2;

            mergeSort(Arr, start, mid);

            mergeSort(Arr, mid + 1, end);

            merge(Arr, start, mid, end);
        }
    }
};

// MAIN METHOD

int main()
{

    int num_elements = 0;

    cout << "Enter a sorting size for the array (between 1 and 16): ";

    while (!(cin >> num_elements) || num_elements > SORT_MAX_SIZE || num_elements < 1)
    {
        // Explain error
        cout << "Error: Enter a number between 1 and 16: ";
        // clear previous input
        cin.clear();
        // discard previous input
        cin.ignore(123, '\n');
    }

    // what type of data do you want to enter?

    cout << "What type of data do you want to enter? " << endl;

    cout << "1: Integer" << endl;

    cout << "2: String" << endl;

    cout << "3: Dollar" << endl;

    int choice;

    cin >> choice;

    int arr_int[num_elements];

    string arr_str[num_elements];

    Dollar arr_dollar[num_elements];

    // Array<string, SORT_MAX_SIZE> stringarray;

    // Array<Dollar, SORT_MAX_SIZE> dollararray;

    // Array<int, SORT_MAX_SIZE> intarray;

    switch (choice)
    {

    case 1:
    {

        for (int i = 0; i < num_elements; i++)
        {

            cout << "Enter element #" << i + 1 << ": ";

            cin >> arr_int[i];
        }

        MergeHelper<int> merger(num_elements);

        merger.mergeSort(arr_int, 0, num_elements - 1);

        print_array(arr_int, num_elements);

        break;
    }

    case 2:
    {

        for (int i = 0; i < num_elements; i++)
        {

            cout << "Enter element #" << i + 1 << ": ";

            cin >> arr_str[i];
        }

        MergeHelper<string> merger(num_elements);

        merger.mergeSort(arr_str, 0, num_elements - 1);

        print_array(arr_str, num_elements);

        break;
    }

    case 3:
    {

        for (int i = 0; i < num_elements; i++)
        {

            cout << "Enter element #" << i + 1 << ": ";

            cout << "Dollars: ";

            int whole;
            cin >> whole;

            double part;
            cin >> part;

            Dollar *buffer = new Dollar(whole, part, "Dollar");

            arr_dollar[i] = *buffer;
        }

        MergeHelper<Dollar> merger(num_elements);

        merger.mergeSort(arr_dollar, 0, num_elements - 1);

        print_array(arr_dollar, num_elements);

        break;
    }
    }
    return 0;
}

I have just written the same code for each of the case but just changed the variable to int, string or dollars. I have utilized the polymorphism as I have used the same name for the function but based on the data type of argument the function is going to decide which one to be applied to get the answer.