
ZOJ Problem Set  1876
An edit step is a transformation from one word x to another word y such that
x and y are words in the dictionary, and x can be transformed to y by adding,
deleting, or changing one letter. So the transformation from dig to dog or from
dog to do are both edit steps. An edit step ladder is a lexicographically ordered
sequence of words w1, w2, ... wn such that the transformation from wi to wi+1
is an edit step for all i from 1 to n1.
The input to your program consists of the dictionary  a set of lower case words in lexicographic order  one per line (the character "" or "'" may also appear). No word exceeds 16 letters and there are no more than 25000 words in the dictionary.
The output consists of a single integer, the number of words in the longest edit step ladder.
Source: University of Waterloo Local Contest 2000.09.23 