Just used STL contaners such as std::map<std::string,T>, std::vector<T>. :)
33 lines of code.

i think its something like this
2
ab\df\fd
df\df
ab
 df
  fd
df
 df
  fd

just consider this condiction:
2
A\A
B\A
the correct output is
A
 A
B
 A
but if you are mistaken, you will output
A
 A

Make sure you don't have spaces after any line

If you use set<A*> or std::sort/std::stable_sort vector/array of pointers, your comparator won't work, because you need special comparator, like this

struct APtrCmp
{
  bool operator()(const A* lhs, const A* rhs) const  { /* implement logic here */ }
};
set<A*, APtrCmp> yourSet;

Good luck! ;)

input#1:

3
a\b\c
a\b\c
b

output#1:

a
_b
__c
b

input#2:
9
a
a\b
a\b\c
a\b\c
a\b\c\d
b\f
b\f\e
b\f\d
b\e

output#2:

a
_b
__c
___d
b
_e
_f
__d
__e

input#3:
3
a
a\b\c\d\e\f
a\b\r\t\p

output#3:
a
_b
__c
___d
____e
_____f
__r
___t
____p

input#4:
4
a\b
b\a
a\c\d
a\c\e

output#4:
a
_b
_c
__d
__e
b
_a


input#5:
4
a
a\b\c\d\e
b\f\e\t
a\b\p

output#5:
a
_b
__c
___d
____e
__p
b
_f
__e
___t

Edited by author 01.10.2007 23:38

Edited by author 01.10.2007 23:42

Edited by author 01.10.2007 23:46

I implemented a prefix tree using pointers and it crashed. I don't know why : for me it worked at max test. But as soon as I moved to an array implementation, it worked!

You have to use StringComparer with parameter StringComparison.Ordinal to pass WA7 in CSharp.

I've got AC in this way.

Solved it with time of 0.5 sec and using "Trie" where I keep the name of each directory as a node.

only Uzbek from ADHAM!!!
input:

4
TUT\TUT\TUT\TUT\TUT\TUT\TUT
TUT\TUT\BUT\BUT\BUT
BUT\TUT\TUT\TUT\TUT
YUT\YUT\BUT\TUT\YUT

output:

BUT
 TUT
  TUT
   TUT
    TUT
TUT
 TUT
  BUT
   BUT
    BUT
  TUT
   TUT
    TUT
     TUT
      TUT
YUT
 YUT
  BUT
   TUT
    YUT

input:
4
A\A\A\A\A\A\A
A\A\A\A\B\B\B\B
A\A\A\A\C\C\C\CB\B\B\V
A\A\A\A\B\C\C\C\C\C\C

output:

A
 A
  A
   A
    A
     A
      A
    B
     B
      B
       B
     C
      C
       C
        C
         C
          C
    C
     C
      C
       CB
        B
         B
          V

Edited by author 19.06.2013 20:29

Can someone give me some tests?
I have WA#10, I don't know what else I can fix to solve this problem.
I used hashes, but I think that my simple algorithm can have collisions, because I make hash mod 10000000;
//sorry for my english.
also I changed algorithm, now I don't use mod. But, I still have WA#10.
I used stack + hash, but, all the same

Edited by author 03.12.2012 19:10

Edited by author 03.12.2012 19:34

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
struct node
{
    int old,child,xiong,last;
}tree[200000];
char word[200000][10],s[110];
char w[20];
int how=0;
int child[20000];
int find(int lao,char wo[20])
{
    for (int i=1;i<=how;i++)
        if (strcmp(word[i],wo)==0 && tree[i].old==lao) return i;
    how++;
    strcpy(word[how],wo);
    return how;
}
void qsort(int l,int r)
{
    int i=l,j=r;
    char x[20]="";
    strcpy(x,word[child[(l+r)/2]]);
    do{
        while (strcmp(word[child[i]],x)<0) i++;
        while (strcmp(x,word[child[j]])<0) j--;
        if (i<=j)
        {
            int t=child[i]; child[i]=child[j]; child[j]=t;
            i++; j--;
        }
    }while (i<=j);
    if (i<r) qsort(i,r);
    if (l<j) qsort(l,j);
    return;
}
void search(int kg,int x)
{
    int a[20000];
    if (x!=0)
    {
        for (int i=1;i<=kg;i++) printf(" ");
        printf("%s\n",word[x]);
    }
    memset(a,0,sizeof(a));
    memset(child,0,sizeof(child));
    int y=tree[x].child;
    while (y!=-1)
    {
        a[0]++;
        a[a[0]]=y;
        y=tree[y].xiong;
    }
    for (int i=1;i<=a[0];i++) child[i]=a[i];
    qsort(1,a[0]);
    for (int i=1;i<=a[0];i++) a[i]=child[i];
    for (int i=1;i<=a[0];i++)
        search(kg+1,a[i]);
}
int main()
{
    int t;
    memset(tree,255,sizeof(tree));
    memset(word,0,sizeof(word));
    scanf("%d",&t);
    getchar();
    while (t-->0)
    {
        memset(s,0,sizeof(s));
        gets(s);
        s[strlen(s)]='\\';
        int len=-1,old=0;
        int ss=strlen(s);
        for (int i=0;i<ss;i++)
        {
            if (s[i]!='\\')
            {
                len++;
                w[len]=s[i];
            }
            else if (s[i]=='\\')
            {
               int x;
               x=find(old,w);
               if (old!=-1)
               {
                     if (tree[x].old==-1)
                     {
                         tree[x].old=old;
                         if (tree[old].child==-1) tree[old].child=x;
                         else tree[tree[old].last].xiong=x;
                         tree[old].last=x;
                     }
               }
               old=x;
               len=-1;
               memset(w,0,sizeof(w));
            }
        }
    }
    search(-1,0);
    return 0;
}


Edited by author 06.02.2012 18:42

INPUT:
a\b
d\a
cc\e
e\d

OTHERWISE,does it have any special situations ?

What is main mistake of programs, which has WA 5?

If you can, write here the hardest or questionable tests, please.

Edited by author 07.02.2011 22:48

type pver=^tver;
     pe=^te;
     te=record
      e:pe;
      ver:pver;
     end;
     tver=record
      s:string;
      e:pe;
     end;
type trec=record
      s:string;
      ver:pver;
     end;
var i,n:word;
    s:string;
    pb,ver:pver;
    fir:boolean;
procedure add(s:string;ver:pver);
var e:pe;
    vt:pver;
begin
 if s='' then exit;
 e:=ver^.e;
 while e<>nil do begin
  if copy(s,1,pos('\',s)-1)=e^.ver^.s then begin
   delete(s,1,pos('\',s));
   add(s,e^.ver);
   exit;
  end;
  e:=e^.e;
 end;
 new(vt);
 vt^.e:=nil;
 if pos('\',s)>0 then vt^.s:=copy(s,1,pos('\',s)-1) else
 vt^.s:=s;
 new(e);
 e^.ver:=vt;
 e^.e:=ver^.e;
 ver^.e:=e;
 if pos('\',s)>0 then begin
  delete(s,1,pos('\',s));
  add(s,vt);
 end;
end;
procedure writ(ver:pver;ur:word);
var a:array [1..600] of trec;
    t:trec;
    kol,u,i:word;
    e:pe;
begin
 kol:=0;
 e:=ver^.e;
 while e<>nil do begin
  inc(kol);
  a[kol].s:=e^.ver^.s;
  a[kol].ver:=e^.ver;
  e:=e^.e;
 end;
 if kol=0 then exit;
 for u:=1 to kol-1 do
 for i:=1 to kol-u do if a[i].s>a[i+1].s then begin
  t:=a[i];
  a[i]:=a[i+1];
  a[i+1]:=t;
 end;
 for i:=1 to kol do begin
{  if not fir then writeln;
  fir:=false;}
  for u:=1 to ur do write(' ');
  writeln(a[i].s);
  writ(a[i].ver,ur+1);
 end;
end;
begin
 new(pb);
 pb^.e:=nil;
 readln(n);
 for i:=1 to n do begin
  readln(s);
  add(s,pb);
 end;
 fir:=true;
 writ(pb,0);
end.

#include <cstdlib>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int n,i,d,j;
string s[505],e[505][90],w,w2,a1,a2;

int main(int argc, char *argv[])
{
   cin>>n;
   for(i=0;i<n;i++)
        cin>>s[i];
   string p;
   p=1;

   w="";
   for(i=0;i<n;i++)
     {
            for(j=0;j<s[i].length();j++)
        if(s[i][j]=='\\')
            s[i][j]=1;
    }
   sort(s,s+n);

    for(i=0;i<n;i++)
        {
            d=0;
            for(j=0;j<s[i].length();j++)
            {w2=s[i][j];
            if(w2.compare(p)==0)
                {
                    d++;

                }
            else
                e[i][d]=e[i][d]+s[i][j];  }
        }
    for(j=0;j<80;j++)
        {if(e[0][j]!="")
            {for(d=0;d<j;d++)
            cout<<" ";

         cout<<e[0][j]<<endl;}

         else
             break;
        }
    for(i=1;i<n;i++)
        {a1="";
         a2="";
            for(j=0;j<80;j++)
                {a1=a1+e[i][j];
                a2=a2+e[i-1][j];

                    if(e[i][j]=="")
                    break;

                else if(a1!=a2)
                {       a1="";
                        a2="";
                        a1=a1+e[i][j];
                        a2=a1+e[i-1][j];
                        for(d=0;d<j;d++)
                        cout<<" ";
                    cout<<e[i][j]<<endl;}
                    }
        }

    return 0;
}

Well,I don't think I often see !~#$%^& in my dictionary...
But I use strcmp directly and it seemed to work.
And a lot of messy structs and pointers made me mad.

I used son-brother to store a tree,so I created a virtual dir called "." in each real dir,that makes programming a bit easier.
Maybe this will somehow help you,or not.

First I save the data like that:
f:array[1..500,1..20]of string[8];
It is Wa 10
Next,I change the way:
f:array[1..500,1..100]of string[10];
Then I AC!!!
I hope that can help you!!!

Could someone give me some tests??

Can you please say what exactly you mean by "lexicographic order"?
As i can see from neerc.ifmo.ru tests, standart C# comparison doesn't fit; and real used order is not so obvious. So i should know what to implement.
Why NTFS_W98 comes after NTFSDOS?
Why ~INTRO comes after CONTENT?

PS: I think that my code is shortest :p
--
using System;
using System.Collections.Generic;

namespace Task1067 {

    class Directory {

        private Dictionary<string, Directory> SubDirs;

        public Directory() {
            this.SubDirs = new Dictionary<string, Directory>();
        }

        public void ProcessSubdirs(Action<KeyValuePair<string, Directory>> Processor) {
            List<string> Keys = new List<string>(this.SubDirs.Keys);
            Keys.Sort();
            foreach(string Key in Keys) {
                Processor(new KeyValuePair<string, Directory>(Key, this.SubDirs[Key]));
            }
        }

        public void AddDir(Stack<string> DirectoryNames) {
            string Name = DirectoryNames.Pop();
            if(!this.SubDirs.ContainsKey(Name)) this.SubDirs[Name] = new Directory();
            if(DirectoryNames.Count > 0) this.SubDirs[Name].AddDir(DirectoryNames);
        }

    }

    class Program {

        private static void PrintSubdirs(Directory Dir, int Depth) {
            Dir.ProcessSubdirs(delegate(KeyValuePair<string, Directory> kvp) {
                Console.WriteLine(new String(' ', Depth) + kvp.Key);
                PrintSubdirs(kvp.Value, Depth+1);
            });
        }

        static void Main(string[] args) {

            int Count = int.Parse(Console.ReadLine());
            Directory RootDir = new Directory();
            for(int i=0; i<Count; i++) {
                List<string> PathComponents = new List<string>(Console.ReadLine().Trim().Split('\\'));
                PathComponents.Reverse();
                RootDir.AddDir(new Stack<string>(PathComponents));
            }

            PrintSubdirs(RootDir, 0);
        }
    }
}