plachu

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

typedef struct data {
    int (*get_rank)(const struct data*);
    char secret[];
} data;

int get_rank(const data* d) {
    return (d->secret[0]);
}

int strcmp(const void * x1, const void * x2)
{
    data* t1 = (data*)x1;
    data* t2 = (data*)x2;
    return ( t1->get_rank(t1) - t2->get_rank(t2));
}

typedef int (*comparator_t)(const void *, const void *);

comparator_t comp = strcmp;

void rank_sort(data* elements[], size_t size) {
    qsort(elements, size, sizeof(data*), comp);
}