Allocating memory for array of pointers of int dynamically
c++, pointers
Solution
In C, `int (* mat)[];` is a pointer to array of `int` with unspecified size (not an array of pointers). In C++ it is an error, the dimension cannot be omitted in C++.
Your question says `new int *[K]` so I assume this is really a C++ question. The expression `new T[n]` evaluates to a `T *` already, there is no implicit conversion.
The code to allocate an array of null pointers using `new` is:
int **mat = new int *[10]();
Then `mat` points to the first one of those. Another option (less commonly used) is:
int * (*mat)[10] = new int *[1][10]();
where `*mat` designates the entire array of 10 pointers.
NB. This sort of code is not useful for anything except demonstration purposes perhaps, whatever you are trying to do has a better solution.
Problem
If I want to dynamically allocate memory for array of pointers of int, how can I achieve this requirement? Suppose I declare an array of pointers of int like this: ``` int (* mat)[]; ``` Is there a way I can allocate memory for K number of pointers dynamically and assign it to mat? If I do ``` mat = new int * [K]; ``` It gives error : `cannot convert 'int**' to 'int (*)[]' in assignment`. I understand this memory allocation is implicitly got converted to int **. Is there any way to allocate memory for above scenario? Even when I try to assignment of statically allocated array of pointers of int to array of pointers of int, like this: ``` int (*mat)[] = NULL; int (* array_pointers)[26]; mat = array_pointers; ``` Compilation gives this error: `cannot convert 'int (*)[26]' to 'int (*)[]' in assignment`. Can someone please explain to me why this is an error or why it should be an error?