Question

I have:

class first{
   private:
   int *array;

   public:
   first(int x){
     array = new int[x][10];
   }

I want to call this class by:

first class1 = new first(10);

Why it doesn’t work ? How to inintialize array by size from constructor ??

Answer 1

Just this is enough:

first class1(10);

new is for when you’re allocating a pointer.

first *class1 = new first(10);

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Furthermore, you have an incompatibility here:

array = new int[x][10];

array is an int*, but new int[x][10] is a 2D array. I’m not sure which one you want.

For the 1D array:

int *array;
array = new int[x];

For the 2D array:

int (*array)[10];
array = new int[x][10];

That said, you might be better off using std::vector.

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Side Note: Since you have memory allocation in the constructor, you should also implement a destructor, copy-constructor, and copy-assignment operator.