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
Swapnil Borse: 2014-12-29 14:24:06

was fun solving this problem :)

rajat arora: 2014-12-17 15:56:17

great question to test knowledge abt modulus

numerix: 2014-11-27 07:39:28

New time limit (set during switch to Cube cluster) is too strict for slower languages. My former Python AC solution (using psyco) cannot pass any more.
The problem is not a hard one, there are 1000+ AC users, so it shouldn't be a problem to increase the TL to allow slower languages to pass.

tranquil: 2014-05-23 17:01:45

getting WA#1 :(
donno what is wrong....mod looks fine to me

P_Quantum: 2014-05-23 10:36:06

Finally AC...don't use long long.

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

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