Finding a Shared Spliced Motif 

http://rosalind.info/problems/lcsq/

A string u is a common subsequence of strings s and t if the symbols of u appear in order as a subsequence of both s and t. For example, "ACTG" is a common subsequence of "AACCTTGG" and "ACACTGTGA".

Analogously to the definition of longest common substring, u is a longest common subsequence of s and t if there does not exist a longer common subsequence of the two strings. Continuing our above example, "ACCTTG" is a longest common subsequence of "AACCTTGG" and "ACACTGTGA", as is "AACTGG".

Given: Two DNA strings s and t (each having length at most 1 kbp) in FASTA format.

Return: A longest common subsequence of s and t. (If more than one solution exists, you may return any one.)