c++ allocate and free dynamic 2d array

To allocate and free a dynamic 2D array in C++, you can follow the steps outlined below:

1. Allocate memory: To create a dynamic 2D array, you need to allocate memory for the rows and columns.

```cpp int numRows = 3; int numCols = 4;

// Allocate memory for the rows int* array = new int[numRows];

// Allocate memory for the columns in each row for (int i = 0; i < numRows; i++) { array[i] = new int[numCols]; } ```

In this example, we allocate memory for a 2D array with 3 rows and 4 columns. We first allocate memory for the rows using the new keyword and store the addresses of the allocated memory blocks in array. Then, we allocate memory for the columns in each row using a loop.

1. Access and modify elements: After allocating memory, you can access and modify individual elements of the 2D array using the row and column indices.

cpp // Access and modify elements array[0][0] = 1; array[1][2] = 3;

Here, we access and modify the element at row 0 and column 0 to be 1, and the element at row 1 and column 2 to be 3.

1. Free memory: Once you are finished using the dynamic 2D array, you should free the memory to prevent memory leaks.

```cpp // Free memory for the columns in each row for (int i = 0; i < numRows; i++) { delete[] array[i]; }

// Free memory for the rows delete[] array; ```

To free the memory, you need to delete the memory blocks for the columns in each row using the delete[] keyword in a loop. Then, you can delete the memory blocks for the rows using delete[].

By following these steps, you can allocate and free a dynamic 2D array in C++.