How to dynamically apply for struct arrays with malloc and access them with subscripts

Eh, subscript access struct members? Real people too;

If you define it: subjecttwo p; with'.'operator accesses its members, such as:

If you define it: subjecttwo p; access its members with ->; Such as: P-> Gearbox

If you define it as: char *p ="hello world !"You can use the subscript to access individual characters, but you are not allowed to modify them.

If you define it as: char str ="hello world !";char *p = str;Individual characters can also be accessed using subscripts, and modification is allowed.

If you define it as: char *p ="hello world !";The individual characters can be accessed with subscripts, allowing modification. Complete.

Memory space is allocated when defining an array structure array.

So when you define it as an array, you can't use malloc anymore.

Choose one or the other.

array, subjecttwo a[1000], it's fine.

If you have to use dynamic application, you may wish to define a subjecttwo* pnext in the structure physical strength, with a linked list...

The application is correct, an array of 10 point types is assigned, and access can be directly using the subscript e.g. pt[0].x , pt[0].y;Access the first few elements, just subscript.

This is the right application.

Access the first struct pt[0]->x,pt[0]->y; the last pt[9]->x, pt[9]->y;

The malloc() function is used to dynamically allocate memory space, and its prototype is: void malloc(size tsize);

Description: (Parameter Description).

size is the amount of memory space allocated in bytes.

Function description] malloc() allocates a specified amount of memory space in the heap to save data. After the function is executed, this memory space is not initialized and its value is unknown. If you want to initialize while allocating memory, you can use the calloc() function.

return value) returns an address pointing to memory when the allocation is successful, and null when it fails.

Operation: Since there may or may not be memory space when memory space is requested, you need to decide for yourself whether the application is successful or not before proceeding.

If the value of size is 0, the return value may or may not be null, depending on the standard library implementation, but the returned pointer should not be referenced again.

Note: The return value type of the function is void, which does not mean that there is no return value or null pointer, but that the returned pointer type is unknown. So when you use malloc(), you usually need to convert the void pointer to the type you want, for example:

# include <

typedefintlistdata；

listdata data; The basic address of the storage space.

data＝（listdata＊）malloc（100＊sizeof（listdata））；

for loop, one by one. Or use setmem for unified initialization.

struct a

struct a *pa = null;

pa = (struct a *)malloc(sizeof(struct a)*n);

n is the number of structures.

Remember to cast memory with free (pa) when you run out.

If there is a student struct, then.

student a=new student[n]() is fine, you can apply as much as you want.

1. You can add pointer class member variables to the struct, and realize the allocation of dynamic arrays in the member function.

2. The following is an example of a class that only implements integer dynamic arrays and does not contain other functions.

class array.

else~array()}

You've opened up this, array = (struct record *)malloc(sizeof(struct record )*num);

It opens up a contiguous space of num*sizeof(struct record) size.

However, when you operate on the array later, try not to use the array form, it is better to use the pointer form.

If you want to increase the number of elements in this array, that is, make this array longer, you can only re-apply for the space size of the new total number, such as increasing m elements.

You can only reapply (struct record *)malloc(sizeof(struct record )*num+m));

Then copy the original data, because the array is a contiguous space, and all the memory must be allocated at once.

array = (struct record *)malloc(sizeof(struct record )*num);This means that you have opened up a space for the array.

If you want to write something in it, you can do this, = , = 3;

#include

#include

void main()

printf("");

If you want to access a two-digit pointer that defines an int a[10][20], defined as int (*p)[20], you need to dynamically assign it, directly int (*p)[20]=malloc(sizeof(a[10][20])).

That is, when defining a two-digit array pointer, the number of rows can be ambiguous, but the number of columns must be explicit, so that the compiler knows that you are defining a row pointer, that is, a two-digit array pointer.

The returned pointer is a structure pointer.

#include

#include

struct ss ;Define the structure int main().

Print s[4].

return 0;

C++ can also be used to allocate units using this method, or you can use new to apply for units.

What do you mean by "applying this struct with a dynamic array", an array of structs?