A common supersequence of strings$s$ and $t$ is said to be a shortest common supersequence
of $s$ and $t$ if there does not exist a shorter common supersequence. That is, a shortest
common supersequence is a common supersequence of minimum length.
For example, although you may verify that although "GACCTAGGAACTC" acts as a common
supersequence of "ACGTC" and "ATAT", it is not a shortest common supersequence of the two strings;
however, "ACGTATC" does serve as a shortest common supersequence of "ACGTC" and "ATAT".
