Multi-dimensional arrays, pointer-to-pointer method
Hi guys!
So I get that a two-dimensional array, when created using a pointer-to-pointer method, is not laid out in memory contiguously, as in the case when the array is declared as int x[5][5];
As a result, we can't use the pointer arithmetic method for locating an element in a two dimensional array created via the pointer-to-pointer method. Yet, C++ allows us to write code that otherwise looks the same.
For example,
int **p_p_x;
p_p_x = new int*[3];
for (int i = 0; i < 3; i++)
{
p_p_x[i] = new int[3];
}
By specifying the 2d array as such, we are still able to reference an element by p_p_x[i][k]. Why is that?
So I get that a two-dimensional array, when created using a pointer-to-pointer method, is not laid out in memory contiguously, as in the case when the array is declared as int x[5][5];
As a result, we can't use the pointer arithmetic method for locating an element in a two dimensional array created via the pointer-to-pointer method. Yet, C++ allows us to write code that otherwise looks the same.
For example,
int **p_p_x;
p_p_x = new int*[3];
for (int i = 0; i < 3; i++)
{
p_p_x[i] = new int[3];
}
By specifying the 2d array as such, we are still able to reference an element by p_p_x[i][k]. Why is that?
Remember the operator precedence rules:
Besides, you don't have to reserve rows separate blocks. You can reserve a single rows*cols block for data and set the pointers on the p_p_x array to point to appropriate elements in that block.
p_p_x[i][k] is same as (p_p_x[i])[k]Besides, you don't have to reserve rows separate blocks. You can reserve a single rows*cols block for data and set the pointers on the p_p_x array to point to appropriate elements in that block.
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