OOP C++ language

Question

I started learning OOP in C++. I try to solve a task like this:

Create a class - a list based on a one-size-fits-all array of integers. Assign a constructor, a destructor, the functions of adding an element to the top (end) of the list, selecting an element from the list by number, sorting the list, showing the elements of the list to the top and to the bottom of the list."

In the delete function, the compiler constantly knocks out the same error:

E0852 the expression must be a pointer to the full type of the object My_4_Project C:\Users\artem\source\repos\Project4\My_4_Project\Source.cpp

Here is my code:

#include <iostream>
#include <algorithm>

using namespace std;

class Array {
  private:
    int* a;
    unsigned int size;
    int b, c = 0, d;
  public:
    Array();
    Array(int s);
    ~Array();
    int& operator[](int index);
    void setarray();
    void getarray();
    void add();
    void delet();
    void sort();
};

Array::Array() {
   size = 10;
   a = new int[size];
   for (size_t i = 0; i != size; i++) {
         a[i] = 0;
   }
}
Array::Array(int s) {
   if (s > 0) {
       size = s;
       a = new int[size];
       for (size_t i = 0; i != size; i++) {
           a[i] = 0;
       }
   }
   else cout << "Size can't be negativ";
}
Array::~Array() {
   delete[]a;
}
int& Array::operator[](int index) {
    if (index <= size) {
        return a[index];
    }
}
void Array::setarray() {
    for (size_t i = 0; i != size; i++) {
          cin >> a[i];
    }
}
void Array::getarray() {
    for (size_t i = 0; i != size; i++) {
        cout << a[i] << " ";
    }
}
void Array::add()
{
     /* ? ? ? */ ;
}
void Array::delet() {
    cin >> b;
    for (int i = 0; i < size; i++)
    {
        if (b == a[i])
            c++;
        if (c > 2) delete a[i];
    }
    cout << c;
}
void Array::sort() {
    int temp;

    for (int i = 0; i < size - 1; i++) {
        for (int j = 0; j < size - i - 1; j++) {
            if (a[j] > a[j + 1]) {
               temp = a[j];
               a[j] = a[j + 1];
               a[j + 1] = temp;
            }
        }
    }
    for (int i = 0; i < size; i++) {
        cout << a[i] << " ";
    }
}

int main() {
    cout << "Enter 10 number`s massive: ";
    Array arr(10);
    arr.setarray();
    cout << endl;
    arr.getarray();
    cout << endl;
    cout << "Sorted massive: ";
    arr.sort();
    cout << endl;
    cout << "Witch symbol you wanna delete?: ";
    arr.delet();
    return 0;
}

Answer 1

The problem is that delete does not work as you think:

• You can delete an object that you previously created with new (new returns a pointer, and delete expect that same pointer).
• You can delete[] something that you previously created with new[]
• But no mixing: you cannot delete an individual element when it was part of an array created with new[]

I will not do the exercise for you but the trick is to:

1. find the index of the duplicate element you want to get rid off,
2. copy every elements afterwards to one index before (i.e. a[j]=a[j+1], of course, making sure that j+1<size )
3. reduce the size by one.

So something like:

void Array::delet() {
     cin >> b;       // better put this in main() and pass it as argument
     for (int i = 0; i < size; i++)
     {
        if (b == a[i]) 
        {            // it'll be more than a single statement
            c++;
            if (c > 2) // found a duplicate 
            {         // NO delete a[i];
                ... // insert a loop to copy the next ones
                    // and reduce the size 
                ...  // EXTRA CAUTION:  in this case the next element 
                     // is again at offset i and not i++
            }
         }
     }
     cout << c;     // ok,  you can display the number of occurences counted
}