create 2d array based on user input

[Tommy98]

thanks done

[sasauke]

You cannot input a constant value, for a constant value cannot be changed and must always be initialized in the code.

What you need to do, since the size isn't a constant value, is to dynamically allocate memory for your array. Doing this with a 1D array is easier: int *arr = new int[size]. With a 2D array, you do the following:

#include <iostream>

int main()
{
	unsigned int rows = 0, cols = 0;

	std::cout << "Rows: ";
	std::cin >> rows;
	std::cout << "Columns: ";
	std::cin >> cols;

	//Dynamically allocate memory for the array
	int **arr = new int*[rows];
	for (unsigned int i = 0; i < rows; i++)
	{
		arr[i] = new int[cols];
	}
	///////////////////////////////////////////////////
	//You can use the array here like you normally would

	for (unsigned int i = 0; i < rows; i++)
	{
		for (unsigned int j = 0; j < cols; j++)
		{
			std::cout << "arr[" << i + 1 << "][" << j + 1 << "]=";
			std::cin >> arr[i][j];
		}
	}

	std::cout << "\nThe array you entered:\n";
	for (unsigned int i = 0; i < rows; i++)
	{
		for (unsigned int j = 0; j < cols; j++)
		{
			std::cout << arr[i][j] << "  ";
		}
		std::cout << "\n";
	}
	/////////////////////////////////////////////////
	//Deallocate the memory after you're done using it
	for (unsigned int i = 0; i < rows; i++)
	{
		delete[] arr[i];
	}
	delete[] arr;

	std::cin.ignore();
	std::cin.get();
	return 0;
}

[Ericool]

@Tommy98 , make sure to read about difference between arrays and dynamic arrays .

[Duthomhas]

Must it be arrays? Why not a vector?

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

int main()
{
  typedef vector <double> row_type;
  typedef vector <row_type> matrix_type;

  matrix_type m;

  unsigned rows, cols;
  std::cin >> rows >> cols;
  for (unsigned r = 0; r < rows; r++)
  {
    row_type row;
    std::copy_n( std::istream_iterator <double> ( std::cin ), cols, std::back_inserter( row ) );
    m.emplace_back( row );
  }
}