Students declarations and implementation of [W2](https://github.com/aut-ce/C-Workshops).

students.c

struct students *students_new(void) {
  struct students *stds = malloc(sizeof(struct students));
  stds->length = 0;
  stds->head = NULL;

  return stds;
}

void students_push_back(struct students *students, struct student *student) {
  struct students_el *el = malloc(sizeof(struct students_el));
  el->next = NULL;
  el->student = student;

  students->length++;

  if (students->head == NULL) {
    students->head = el;
  } else {
    struct students_el *p = students->head;

    while (p->next != NULL) {
      p = p->next;
    }

    p->next = el;
  }
}

void students_remove(struct students *students, int index) {
  struct students_el *el = students->head;

  if (index == 0) {
    students->head = el->next;
    free(el->student);
    free(el);
  } else {
    int i = 0;
    while (el && i + 1 < index) {
      el = el->next;
      i++;
    }
    if (i + 1 == index) {
      struct students_el *p = el->next->next;
      free(el->next->student);
      free(el->next);
      el->next = p;
    }
  }
}

int students_search_id(struct students *students, const char *id) {
  int index = -1;
  int i = 0;

  struct students_el *p = students->head;
  while (p) {
    if (strcmp(p->student->id, id) == 0) {
      index = i;
      break;
    }
    i++;
    p = p->next;
  }

  return index;
}

students.h

struct student {
    char name[256];
    char id[8];
};

struct students {
    int length;
    struct students_el *head;
};

struct students_el {
    struct student *student;
    struct students_el *next;
};

struct students *students_new(void);

void students_push_back(struct students *students, struct student *student);

void students_remove(struct students *students, int index);

int students_search_id(struct students *students, const char *id);