How to increment the index of an unlimited array?

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How can I increment an array within a structure?

This is my structure:

struct list {
char name[50];
int products_list[]; } LIST[10];

I wanted to know the current number of elements in the array (products_list) to add more products with the right index.

My problem is: I use the scanf to get the user products, so they can be unlimited. I tried using sizeof function but it didn’t work because it didn’t add right the products index’s.

posicao_atual = (sizeof(LISTA[opcao_lista].produtos_listas) / sizeof(int) + 1);

Thank you.

c array struct auto-increment

  • Ah, and by the way, what’s stopping you from putting a counter like int within the structure to tell how many items are filled?

  • My problem is, I have several shopping lists. You can insert 3 products into one, exit the product insertion area and return at any time. That’s when I need to know, that exactly on that list there are 3 products. With the counter I would increment to any list.

  • Try to suffer more in the problem. What is your goal at the end of all this?

  • Ué, just create a function to add items in the list, receiving it as parameter and the item to be added. Then, you increment the variable that indicates the quantity and enter. I remember making such lists in the discipline of Data Structure, and this problem was solved like this.

  • 1

    @Antoniofreitas the two accounts are yours, right? You want us to put them together? Which of the two must survive?

1 answer

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include a variable with the size of the list: unsigned int product_list_size.

typedef struct {
    char name [50];
    unsigned int product_list_size;
    int products_list [];
} list_t;

// ...

list_t list [10];
list.product_list_size = 0;
// Inicialização da lista...

When including a new product, increment the counter. list_number is the number on the list.

list [list_number].product_list_size++;

Option 1 of Count

Use this counter for memory allocation. If you are going to remove a product from the list, simply decrement and allocate the products in the new positions.

Option 2 of Count

When deleting an item from the list, set to how -1 (position is the position of the product in the list), without decreasing the product_list_size. No need to relocate memory.

list [list_number].products_list [position] = -1;

To count just go through the list and discard the negative values

unsigned int product_list_size = 0;

for (unsigned int _position; _position < list [list_number].product_list_size; _position++) {
    if (list [list_number].products_list [_position] > 0)
        product_list_size++;

Do not forget that the maximum size of the list will be the maximum size of the integer, according to the platform.

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