ls_r.h

#include<bits/stdc++.h>
#include <unistd.h>
#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <sys/stat.h>
#include <stdlib.h>
using namespace std;
void filewrite(char *c,char * f)
{
FILE *fptr;

   fptr = fopen(f, "a");
   if(fptr == NULL)
   {
      printf("Error!");
      exit(1);
   }
   
  // printf("Enter a sentence:\n");
  // gets(sentence);

   fprintf(fptr,"%s\n",c);
   fclose(fptr);
}
void ls_r(char *dir,char *file_name)
{
DIR *dp;
struct dirent *entry;
string s=dir;
unordered_map< string, list< string > > adj;
struct stat statbuf;
if((dp = opendir(dir)) == NULL) {
fprintf(stderr,"cannot open directory: %s\n", dir);
return;
}
//adj[s]
chdir(dir);

while((entry = readdir(dp)) != NULL) {
lstat(entry->d_name,&statbuf);
if(S_ISDIR(statbuf.st_mode)) {
/* Found a directory, but ignore . and .. */
if(strcmp(".",entry->d_name) == 0 || 
strcmp("..",entry->d_name) == 0)
continue;

//printf("%*s%s/\n",depth,"",entry->d_name);
/* Recurse at a new indent level */
adj[s].push_back(entry->d_name);
ls_r(entry->d_name,file_name);
//filewrite(entry->d_name,file_name);
}
else
{ 
  adj[s].push_back(entry->d_name);
	//filewrite(entry->d_name,file_name);
	//printf("%*s%s\n",depth,"",entry->d_name);
}
}
chdir("..");
closedir(dp);
for (auto itr1=adj.begin();itr1!=adj.end();itr1++) {
        string vertex = itr1->first;
        list<string> adjv = itr1->second;
        list<string>::iterator itr = adjv.begin();
         
        filewrite((char*)vertex.c_str(),file_name);
          
        while (itr != adjv.end()) {
           string t=*itr;
           filewrite((char*)t.c_str(),file_name);
           itr++;
        }
         
        //cout << endl;
    }
}