Question

I am comfortable with structures that contains one item per variable. But i am struggling to manage structure that contains multiple items in one variable (within a matrix). it's in C language.

for example this structure :

   struct resume{
char *name;
char *job;
char school*;
int counter_resume;

}resume;

i want to create functions that are able to dynamically allocate memory so it can add multiple persons resume without knowing how many they are going to be in the beginning. Lets say we have Bob . Bob worked as a fireman, postman, and truck driver. So there is 3 items in the Jobs variable for Bob. let say he went to school to Marveric and Standford. We should be able to add more persons in the same structure using the functions. for example the main look like this :

nb: feel free to give more knowledge, suggestions, or any useful advices or  information needed for me to master this particular subject.

int main()
{
struct resume *Bob = malloc(sizeof(struct resume));

add_name(Bob,"Bob");

add_job(Bob, "Postman");
add_job(Bob, "Truck driver");
add_job(Bob, "fireman");

add_school(Bob, "Standford University");
add_school(Bob, "Chicago business school");

print_single_resume(Bob); // print Bob resume
print_all_resume(); // print all of the resumes

free_memory(bob); // function that free the memory allocated

free_all(); // function that free the memory allocated for all the persons
}

Answer 1

We can use arrays to store more than one values for the same data type. Here we need to keep the count of elements in the array. The initial count is 0 and when we add elements to the array, increment the count by 1. The array index starts with 0. We can add each element at the specified index of the array. We need to specify the maximum size of the array at the time of declaration.

#include<stdio.h>
#include<stdlib.h>
struct resume{
    char *name;
    char *job[10];    // array of jobs(maximum 10 jobs
    int jobCount;     // count of jobs
    char *school[10]; // array of school(maximum 10 schools)
    int schoolCount; // count of schools
    int counter_resume;
}resume;

// array of resume and the count of resumes
struct resume* resumes[10];
int resumeCount = 0;

// function to add name to a resume
void add_name(struct resume *r, char* name){
    r->name = name;
}
// function to add job to a resume
void add_job(struct resume *r, char* job){

    r->job[r->jobCount++] = job;
}
// function to add school to a resume
void add_school(struct resume *r, char* school){
    r->school[r->schoolCount++] = school;
}
// function to print a resume
void print_single_resume(struct resume *r){
    printf("\nName: %s\n", r->name);
    printf("Jobs: ");
    int i;
    for(i=0; i<r->jobCount-1; i++){
        printf("%s,", r->job[i]);
    }
    printf("%s\n", r->job[i]);
    printf("Schools: ");
    for(i=0; i<r->schoolCount-1; i++){
        printf("%s,", r->school[i]);
    }
    printf("%s\n", r->school[i]);
}
// function to print all resumes
void print_all_resume(){
    int i;
    for(i=0; i<resumeCount; i++){
        print_single_resume(resumes[i]);
    }
}
// function to free memory of a resume
void free_memory(struct resume *r){
    free(r);
}
// function to free memory of all resumes
void free_all(){
    int i;
    for(i=0; i<resumeCount; i++){
        free_memory(resumes[i]);
    }
}
int main()
{
    struct resume *Bob = malloc(sizeof(struct resume));

    add_name(Bob,"Bob");

    // initialize counts to 0
    Bob->jobCount = 0;
    Bob->schoolCount = 0;

    add_job(Bob, "Postman");
    add_job(Bob, "Truck driver");
    add_job(Bob, "fireman");

    add_school(Bob, "Standford University");
    add_school(Bob, "Chicago business school");

    // add Bob to resumes
    resumes[resumeCount++] = Bob;

    struct resume *Jay = malloc(sizeof(struct resume));
    // initialize counts to 0
    Jay->jobCount = 0;
    Jay->schoolCount = 0;
    add_name(Jay,"Jay");
    add_job(Jay, "Postman");
    add_school(Jay, "Standford University");
    // add Jay to resumes
    resumes[resumeCount++] = Jay;

    printf("\nBob's resume:");
    print_single_resume(Bob); // print Bob resume

    printf("\n\nAll resumes:\n");
    print_all_resume(); // print all of the resumes

    free_memory(Bob); // function that free the memory allocated

    free_all(); // function that free the memory allocated for all the persons
}

Output