Given list of words in the order as in the dictionary, find the order of the alphabets.

Example:
 
Suppose you are given words in the same order as in the dictionary like a, ant, ball, cat, do, dog, fog, frock etc.
From these words you know that there are alphabets a, n, t, b, l, c, d, o, g, f, r, k.
You don't know the order of these alphabets before hand.
You will have to find the order of these alphabets based on the order of the given words.
 
Some Analysis :
 
From a and ant you cannot make out anything.
From ant and ball you can make out that a comes before b in the order.
From ball and cat you can make out that b comes before c in the order.
From cat and do you can make out that c comes before d in the order.
From do and dog you cannot make out anything.
From dog and fog you can make out that d comes before f in the order.
From fog and frock you can make out that o comes before r in the order.
From these clues you should make out the order of the alphabets.
Not necessarily you will be given all the dictionary words, but the words which are sufficient enough to make out the order of the alphabets.
You can always say you cannot make out the order if the words given are not sufficient.

Why don't make hands little dirty  , give it a try , shoot me comment :)

Given a php source file which contains a few classes defined in it. ,print the class hierarchy in the given desired format.

In PHP, there is concept of single class inheritance i.e. a new class can extend an existing class. You are given a php source file which contains a few classes defined in it. You have to print the class hierarchy in the given desired format.
For example, classes in php source file are A, B extending A, C extending B, D extending A, E.
The output should look like:

A
B
C
D
E