struct-C中字符串的二维数组

Question

I am trying to make a two dimensional array in a struct using pointer since I am new to c and get quite confuse in the topic of pointer. Help please!

struct course
{
    char *coursecode;
    char *coursesession[5];
};

int main()
{

    int n = 0;
    int numSession = 0;
    struct course *main = malloc(sizeof(struct course));



    printf("Enter the course code and the session in this order:");
    scanf("%s", main->coursecode);
    printf("Enter the number of session required:");
    scanf("%d", &numSession);
    for (int i = 0; i < numSession; ++i)
        {
            printf("Enter the session code (M1...):");
            scanf("%s", main->coursesession[i]);
        }
    ++n;
}

Answer 1

You've declared coursecode to be a pointer to char , but you need to allocate space for it, which you can do with malloc .

And you've declared coursesession to be an array of 5 pointers to char . You need to allocate space for all 5 pointers, again with malloc .

Alternatively, you could declare both of them as arrays, eg

struct course
{
    char coursecode[100];
    char coursesession[5][100];
};

This declares coursecode to be an array of 100 char , and coursesession to be an array of 5 arrays of 100 char . Obviously you could adjust the 100 to whatever you need, but the storage size would be fixed regardless.

Answer 2

You can modify code like this

#include <stdio.h>
#include<stdlib.h>


struct course
{
   char *coursecode;
   char *coursesession[5];
};

int main()
{

    int n,i = 0;
    int numSession = 0;
    struct course main;

    main.coursecode = (char *)malloc(100*sizeof(char));
    printf("Enter the course code and the session in this order:");
    scanf("%s", main.coursecode);
    printf("Enter the number of session required:");
    scanf("%d", &numSession);
    for (i = 0; i < numSession; ++i)
    {
        printf("Enter the session code (M1...):"); 
        main.coursesession[i] = (char *)malloc(100*sizeof(char));
        scanf("%s", main.coursesession[i]);
    }
    ++n;
    free(main.coursecode);
    for (i = 0; i < numSession; ++i){
        free(main.coursesession[i]);
    }
}