使用循环在 C 中创建新结构

Question

Here, I have created a structure of student having name, roll no, marks, etc as their members. So, what I wanted to do was create a new struct every time it iterates through a loop and saving data in it as it loops through.

So, I created a variable stdname that changes it's value every iteration and use it as a way to name a new student but it's not working. I am fairly new to C and I don't know what is wrong with my code here.

#include <stdio.h>

struct Marks

{
    int phy;
    int chem;
    int math;
};

struct Student{
    char name[50];
    int rollN0;
    char remarks[100];
    struct Marks marks;
};

int main()
{
    for (int i=0; i<10; i++)
    {
        char stdname[50];
        sprintf(stdname,"student%d",i+1);
        struct Student stdname;
        printf("Enter the following data of Student No. %d:\n", i+1); 
        //taking data from user and storing 
    }
}

Answer 1

I propose you to solve your problem by implementing a systeme of linked list or tabs. I personnaly perfere linked list because when your code will evolute it's going to be easier to used the list in my pov.

So in the code you will see in your structure i add a next pointer this one will store the adresse of another student, if next is NULL then we can affirm there is no more student and we can stop crawling throught the list.

the function add use this principe; she goes to the tail of the list then replace the next with the adresse of the new student structure. And because the next of the new structure is NULL this process it re-usable

The function create_new_node is only data initation and memory allocation. It looks very ugly because i don't realy know what you want store.

❗ I didn't test this code and it's not optimised at all ❗

#include <stdio.h>
#include <stdlib.h> // for malloc function

struct Marks

{
    int phy;
    int chem;
    int math;
};

struct Student{
    char name[50];
    int rollN0;
    char remarks[100];
    struct Marks marks;
    struct Student* next;  // I had this
};
/// new ///
void add_node_to_list(struct Student* node, struct Student* list)
{
    while (list->next != NULL)
        list = list->next;
    list->next = node;
}

struct Student* create_new_node(struct Student data)
{
    struct Student* new_node = malloc(sizeof(struct Marks));

    if (!new_node)
        return NULL;

    new_node->name = data.name;
    new_node->rollN0 = data.rollN0;
    new_node->remarks = data.remarks;
    new_node->marks = data.marks;
    new_node->next = NULL;

    return new_node;
}
/// end-new ///

int main(void /* new */)
{
    struct Student* list = NULL;
    struct Student* new_node = NULL;

    for (int i=0; i<10; i++)
    {
        char stdname[50];
        sprintf(stdname,"student%d",i+1);
        /// new ///
        if (!list) {                        // first the first element
            list = create_new_node((struct Marks) {stdname, 0, "\0", {0, 0, 0}, NULL}); 
            if (!list)        // check for malloc errors
                return 1;
        } else {                            // every time there is a new student
            new_node = create_new_node((struct Marks) {stdname, 0, "\0", {0, 0, 0}, NULL});
            if (!new_node)  // check for malloc errors
                return 1;
            add_node_to_list(new_node, list);
        }
        /// end-new ///
        printf("Enter the following data of Student No. %d:\n", i+1);
        //taking data from user and storing
    }
    return 0; // new: your main should always return a value. Compile with W flags see: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
}

Here is my propostion, Notice me if i had been clumsy, i'm a new user on stack.

Also feel free to ask question or fix my own error

Hope I helped you