Student Sorting - School HW - 24/04/2019

students_sort.c

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

#define stringize(s) #s

enum subjects {
    maths,
    history,
    programming,
    geography,
    count
};

struct student {
    int marks[count];
    char name[];
};

typedef unsigned char grade;
typedef const struct student** student_doubleptr;

struct student *alloc_student(const char *name, grade _maths, grade _history, grade _programming, grade _geography) {
    struct student *res = calloc(1, sizeof(struct student) + strlen(name) + sizeof "");
    if (!res)
        return 0;
    strcpy(res->name, name);
    res->marks[maths] = _maths;
    res->marks[history] = _history;
    res->marks[programming] = _programming;
    res->marks[geography] = _geography;
    return res;
}

int compare_programming(const void *p1, const void *p2) {
    student_doubleptr s1 = (student_doubleptr) p1,
            s2 = (student_doubleptr) p2;

    if ((**s1).marks[programming] > (**s2).marks[programming])
        return -1;
    if ((**s1).marks[programming] < (**s2).marks[programming])
        return 1;
    return 0;
}

void print_index(struct student *index[], const int subject, const unsigned class_size) {
    for (unsigned i = 0; i < class_size; ++i)
        printf("%s has %d.\n", index[i]->name, index[i]->marks[subject]);
}

int main(int argc, const char const *argv[]) {
    const unsigned CLASS_SIZE = 4;

    struct student *all[] =
            {
                    alloc_student("Georgi Ivanov", 4, 6, 2, 5),
                    alloc_student("Petyr Borisov", 5, 3, 4, 4),
                    alloc_student("Filip Kostadinov", 5, 3, 5, 4),
                    alloc_student("Petyo Atanasov", 2, 3, 6, 4)
            };


    struct student *programming_index[CLASS_SIZE];
    memcpy(programming_index, all, sizeof all);
    qsort(programming_index, CLASS_SIZE, sizeof *programming_index, compare_programming);

    printf("sorting by %s...\n", stringize(programming));
    print_index(programming_index, programming, CLASS_SIZE);

    return 0;
}