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

#ifndef LOOPCOUNT
#define LOOPCOUNT 1
#endif

typedef struct node_t {
    int count;
    struct node_t *ascii[256];
} node_t;

node_t *root;
int max_depth;

void show_list(node_t *node, char *word, int depth)
{
    int i;
    if (node->count) {
        word[depth] = '\0';
        for (i = 0; i < node->count; i++) {
            puts(word);
        }
    }

    for (i='a'; i <= 'z'; i++) {
        if (node->ascii[i]) {
            word[depth] = i;
            show_list(node->ascii[i], word, depth+1);
        }
    }
    for (i='A'; i <= 'Z'; i++) {
        if (node->ascii[i]) {
            word[depth] = i;
            show_list(node->ascii[i], word, depth+1);
        }
    }
}

void show_list_reverse(node_t *node, char *word, int depth)
{
    int i;
    for (i='Z'; i >= 'A'; i--) {
        if (node->ascii[i]) {
            word[depth] = i;
            show_list_reverse(node->ascii[i], word, depth+1);
        }
    }
    for (i='z'; i >= 'a'; i--) {
        if (node->ascii[i]) {
            word[depth] = i;
            show_list_reverse(node->ascii[i], word, depth+1);
        }
    }

    if (node->count) {
        word[depth] = '\0';
        for (i = 0; i < node->count; i++) {
            puts(word);
        }
    }
}

void free_node(node_t *node) {
    int i=0;
    for (i=0; i < sizeof(node->ascii)/sizeof(node->ascii[0]); i++) {
        if (node->ascii[i]) {
            free_node(node->ascii[i]);
        }
    }
    free(node);
}

void insert_word(node_t *node, char *word, int depth)
{
    if (*word == '\0') {
        node->count++;
        if (depth > max_depth) {
            max_depth = depth;
        }
        return;
    }

    if (!node->ascii[(int)*word]) {
        node->ascii[(int)*word] = (node_t *)calloc(1, sizeof(node_t));
    }
    insert_word(node->ascii[(int)*word], word + 1, depth + 1);
}

char *read_file(char *fname)
{
    FILE *fp;
    size_t filesize;
    char *buff;

    fp = fopen(fname, "rb");
    fseek(fp, 0, SEEK_END);
    filesize = ftell(fp);
    buff = (char *)calloc(1, filesize + 1);
    buff[filesize] = '\0';
    fseek(fp, 0, SEEK_SET);
    fread(buff, filesize, 1, fp);
    fclose(fp);

    return buff;
}

void task(char *fn, int is_asc)
{
    char *buff;
    char *token;

    buff = read_file(fn);

    root = (node_t *)calloc(1, sizeof(node_t));

    token = strtok(buff, "\n");
    while (token) {
        insert_word(root, token, 0);
        token = strtok(NULL, "\n");
    }

    {
        char *word_buf = (char *)malloc(max_depth + 1);
        if (is_asc) {
            show_list(root, word_buf, 0);
        } else {
            show_list_reverse(root, word_buf, 0);
        }

        free(word_buf);
    }

    free_node(root);
    free(buff);
}

int main(int argc, char **argv)
{
    int is_asc = 1;

    if (argc != 2 && argc != 3) {
        fprintf(stderr, "USAGE: %s filename [desc]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    is_asc = !(argc == 3 && !strcmp(argv[2], "desc"));

    {
        int loopcount;
        for (loopcount=0; loopcount < LOOPCOUNT; loopcount++) {
            task(argv[1], is_asc);
        }
    }

    return 0;
}