#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
int n = 0;
void readalldir(char *dirname, char **txtdata){
    DIR *dir = opendir(dirname);
    struct dirent *fi;
    while(fi = readdir(dir)){
        if(fi->d_type==DT_DIR && fi->d_name[0]!='.'){
            int senlen = strlen(dirname);
            strcat(dirname, "/");
            strcat(dirname, fi->d_name);
            readalldir(dirname, txtdata);
            dirname[senlen] = '\0';
        }
        if(fi->d_type==DT_REG){
            int senlen = strlen(dirname);
            strcat(dirname, "/");
            strcat(dirname, fi->d_name);
            FILE *txt = fopen(dirname, "r");
            txtdata[n] = malloc(sizeof(char) * 50);
            fgets(txtdata[n], 50, txt);
            strcat(txtdata[n], "\n");
            n++;
            fclose(txt);
            dirname[senlen] = '\0';
        }
    }
    closedir(dir);
}
void freetxtdata(char **txtdata){
    int i;
    for(i = 0; i<n; i++){
        free(txtdata[i]);
    }
    free(txtdata);
}
void writefile(char **txtdata){
    FILE *txt = fopen("result.txt", "w");
    int i;
    for(i = 0; i<n; i++){
        fputs(txtdata[i], txt);
    }
}
int comper(const void *a, const void *b){
    long int aa = atoi(*((char**) a));
    long int bb = atoi(*((char**) b));
    if(aa > bb){
        return 1;
    }
    if(aa < bb){
        return -1;
    }
    else{
        return 0;
    }
}
int main(){
    char dirname[50] = "./root";
    char **txtdata = malloc(sizeof(char*) * 3000);
    readalldir(dirname, txtdata);
    qsort(txtdata, n, sizeof(char*), comper);
    writefile(txtdata);
    freetxtdata(txtdata);
    return 0;
}