sorting-array-of-strings.c

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) < (b) ? (b) : (a))

int lexicographic_sort(const void *a, const void *b) {
    const char **ia = (const char **)a;
    const char **ib = (const char **)b;
    return strcmp(*ia, *ib);
}

int lexicographic_sort_reverse(const void *a, const void *b) {
    return lexicographic_sort(b, a);
}

int sort_by_length(const void *a, const void *b) {
    const char **ia = (const char **)a;
    const char **ib = (const char **)b;
    int ret;
    
    if ((ret = strlen(*ia) - strlen(*ib)) == 0)
        return lexicographic_sort(a, b);
    else
        return ret;
}

int sort_by_number_of_distinct_characters(const void *a, const void *b) {
    const char **ia = (const char **)a;
    const char **ib = (const char **)b;
    int sum_a = 0, sum_b = 0;
    int count_a[26];
    int count_b[26];
    
    for (int i = 0; i < 26; i++) {
        count_a[i] = 0;
        count_b[i] = 0;
    }
    
    for (int i = 0; i < strlen(*ia); i++)
        count_a[(*ia)[i] - 'a'] = 1;
    
    for (int i = 0; i < strlen(*ib); i++)
        count_b[(*ib)[i] - 'a'] = 1;
    
    for (int i = 0; i < 26; i++) {
        sum_a += count_a[i];
        sum_b += count_b[i];
    }
    
    if ((sum_a - sum_b) == 0)
        return lexicographic_sort(a, b);
    else
        return (sum_a - sum_b);
}

void string_sort(char **arr, const int len, int (*cmp_func)(const char *a, const char *b)) {
    qsort(arr, len, sizeof(char *), cmp_func);
}