char example[10];
example is an array of 10 chars. Depending on context, it has automatic or static storage. The size can only be compile time constant. The array is destroyed and deallocated automatically.
char* example = new char[10];
example is a pointer. It is not an array. It points to first element of an array in dynamic storage. The size of dynamic array can be determined at runtime. The array is not destroyed and deallocated automatically. If not deallocated, the memory will leak.
Dynamic allocation is generally slower than static or automatic. On the other hand, the amount of memory available for automatic storage is typically very limited.
Bare owning pointers should be avoided. Best practice is to use a smart pointer or a RAII container such as std::vector when dynamic array is needed.
char example[10];
example is an array of 10 chars. Depending on context, it has automatic or static storage. The size can only be compile time constant. The array is destroyed and deallocated automatically.
char* example = new char[10];
example is a pointer. It is not an array. It points to first element of an array in dynamic storage. The size of dynamic array can be determined at runtime. The array is not destroyed and deallocated automatically. If not deallocated, the memory will leak.
Dynamic allocation is generally slower than static or automatic. On the other hand, the amount of memory available for automatic storage is typically very limited.
Bare owning pointers should be avoided. Best practice is to use a smart pointer or a RAII container such as std::vector when dynamic array is needed.
This:
char example[10];
Declares example as an array of char containing 10 elements. If declared at file scope, this array will typically reside in the data segment, while if it is declared at block scope it will typically reside on the stack.
In contrast, this:
char* example = new char[10];
Declares example as a pointer to char, and initializes it with a pointer to dynamically allocated memory which points to the first member of a 10 member array of char. This dynamically allocated memory typically resides on the heap.
Note also that new is specific to C++.
Videos
It is an array of 'n' pointers, for which memory can be allocated and initialized in loop. If n is 3, it is an array of 3 elements and each is pointer to int, can point to set of array of integer values like below.
matrix[0] -> Ox001 points to array of int [ 1 2 3 4]
matrix[1] -> Ox017 [ 5 6 7 8]
matrix[2] -> Ox024 [ 9 10 11 12]
Sample code like this
int **m = new int*[3];
for(auto i=0; i < 3; i++)
{
m[i] = new int[3];
for(auto j=0; j < 3; j++)
m[i][j] = 0;
}
for(auto i=0; i < 3; i++)
{
m[i] = new int[3];
for(auto j=0; j < 3; j++)
cout << m[i][j];
cout << "\n";
}
for instance there is cricket team and you need
Since you have Cricket* team;, this indicates you have one of two possible
situations:
1) a pointer to a single CricketPlayer (or any derived) type
2) a pointer to an array of CricketPlayer (but not derived) types.
What you want is a pointer to an array of CricketPlayer or derived types. So you
need the **.
You'll also need to allocate each team member individually and assign them to the array:
// 5 players on this team
CricketPlayer** team = new CricketPlayer*[5];
// first one is a bowler
team[0] = new Bowler();
// second one is a hitter
team[1] = new Hitter();
// etc
// then to deallocate memory
delete team[0];
delete team[1];
delete[] team;
In your query,
It can be understood as
int *matrix[]=new int*[n];
SO there are n pointers pointing to n places.
Because
int *foo;
foo=new int[5];
will also create 5 consecutive places but it is the same pointer.
In our case it is array of pointers
So I don't consider myself a CS noob by any means and have wrangled my fair share of systems, but also find myself forgetting my CS classes a bit and was surprised when I pondered this I didn't have a clear answer. So, in C/C++ (assuming a non-optimizing compiler) I know when we have a declaration like int stackVar = 5; that will probably get placed either in a register or on in-memory stack. However, when you call new, you always get a pointer back, because from what I understand, new will mean it always goes to heap. Why is it this way? It seems to me that instantiating makes sense for larger objects because having a pointer to them is less expensive than loading the object itself. But when then do we put things on stack, or is that only primitive data types? What does "instantiating" actually mean in the context of saying Request* r = new Request() for some web API versus the above int r = 5 example? How are the two different?
Hi, C# beginner here, can someone explain to me why I should use “new” when creating an array instead of just giving it values from the beginning? Thanks :)
In the new Standard for C++ (C++11), you can do this:
int* a = new int[10] { 1,2,3,4,5,6,7,8,9,10 };
It's called an initializer list. But in previous versions of the standard that was not possible.
The relevant online reference with further details (and very hard to read) is here. I also tried it using GCC and the --std=c++0x option and confirmed that it works indeed.
You can use memcpy after the allocation.
int originalArray[] ={1,2,3,4,5,6,7,8,9,10};
int *array = new int[10];
memcpy(array, originalArray, 10*sizeof(int) );
I'm not aware of any syntax that lets you do this automagically.
Much later edit:
const int *array = new int[10]{1,2,3,4,5,6,7,8,9,10};