DSUBSEQ - Distinct Subsequences

Given a string, count the number of distinct subsequences of it ( including empty subsequence ). For the uninformed, A subsequence of a string is a new string which is formed from the original string by deleting some of the characters without disturbing the relative positions of the remaining characters.
For example, "AGH" is a subsequence of "ABCDEFGH" while "AHG" is not.


First line of input contains an integer T which is equal to the number of test cases. You are required to process all test cases. Each of next T lines contains a string s.


Output consists of T lines. Ith line in the output corresponds to the number of distinct subsequences of ith input string. Since, this number could be very large, you need to output ans%1000000007 where ans is the number of distinct subsequences.




Constraints and Limits

T ≤ 100, length(S) ≤ 100000
All input strings shall contain only uppercase letters.

hide comments
Nadbor Drozd: 2014-01-22 11:31:06

linear time and still time limit exceeded. Tried switching from python to java and c++, but couldn't get them even past compilation on with these ancient versions of the language. I give up

Savan Popat: 2014-01-08 14:49:35

anybody please explain for which case answer will be negative.

Ankit Jain: 2014-01-02 09:44:27

ok..so after reading the previous comments...googled a bit about modulus...modified the solution...got ac.....but still unable to understand as to which test case gives us a negative value of dp[] because of which all this trouble is occuring...thanks in advance to anybody willing to explain this weird bahviour...

Rishabh Saxena: 2013-12-17 23:58:11

for those getting Wrong Answer #1.....they should look into the fact that they can get negative answer!!
I just made some changes in my mod function to make it positive and it got accepted... :)

aqfaridi: 2014-04-08 23:55:38

good problem. think dp ..

Last edit: 2013-05-31 11:04:48
hitachi: 2013-05-15 02:43:16

for those getting WA#1...problem is i think in the mod operation

Last edit: 2013-05-15 02:45:16
:-): 2013-04-24 15:36:17

awesome problem

codecracker: 2013-04-01 23:18:55

mod(x)=x%m working fine...no need for increasing overhead

(^@_^@): 2013-04-01 22:29:51

Last edit: 2013-05-12 19:34:08
_maverick: 2013-03-23 16:08:57

wow DP problems fill ma life a gud classic one...
and don't forget to mod costed me one WA ;)

Added by:Ajay Somani
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: CPP
Resource:CodeCraft 08, Problem Setter: Jin Bin