Given two sequences S, T, count number of unique ways in sequence S, to form a subsequence that is identical to the sequence T.
Subsequence : A subsequence of a string is a new string which is formed from the original string by deleting some (can be none ) of the characters without disturbing the relative positions of the remaining characters. (ie,
"ACE"is a subsequence of
S = "rabbbit"
T = "rabbit"
3. And the formations as follows:
S1= "ra_bbit" S2= "rab_bit" S3="rabb_it"
"_" marks the removed character.