Sphere Online Judge

SPOJ Problem Set (classical)

394. Alphacode

Problem code: ACODE

Alice and Bob need to send secret messages to each other and are discussing ways to encode their messages:

Alice: “Let’s just use a very simple code: We’ll assign ‘A’ the code word 1, ‘B’ will be 2, and so on down to ‘Z’ being assigned 26.”

Bob: “That’s a stupid code, Alice. Suppose I send you the word ‘BEAN’ encoded as 25114. You could decode that in many different ways!”

Alice: “Sure you could, but what words would you get? Other than ‘BEAN’, you’d get ‘BEAAD’, ‘YAAD’, ‘YAN’, ‘YKD’ and ‘BEKD’. I think you would be able to figure out the correct decoding. And why would you send me the word ‘BEAN’ anyway?”

Bob: “OK, maybe that’s a bad example, but I bet you that if you got a string of length 5000 there would be tons of different decodings and with that many you would find at least two different ones that would make sense.”

Alice: “How many different decodings?”

Bob: “Jillions!”

For some reason, Alice is still unconvinced by Bob’s argument, so she requires a program that will determine how many decodings there can be for a given string using her code.


Input will consist of multiple input sets. Each set will consist of a single line of at most 5000 digits representing a valid encryption (for example, no line will begin with a 0). There will be no spaces between the digits. An input line of ‘0’ will terminate the input and should not be processed.


For each input set, output the number of possible decodings for the input string. All answers will be within the range of a 64 bit signed integer.






Added by:Adrian Kuegel
Time limit:0.341s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel Pentium G860 3GHz)
Resource:ACM East Central North America Regional Programming Contest 2004

hide comments
2014-11-09 11:55:33 Ashish
Silly mistake of length caused me 3 WA
2014-10-05 19:17:17 Dima
The "29" test case seems to be missing.

I passed with http://ideone.com/o59QDg but also passed with http://ideone.com/6UEthP. Diff the sources to locate an obvious bug, which is challenged by "29".


Last edit: 2014-10-05 19:17:55
2014-10-04 14:51:00 Subham Nagar
phew! finally AC! requires thinking! :)
Nice Sum! I just love DP!
2014-10-02 20:01:54 7Bubble
it made me smile..
2014-09-29 07:17:07 Ashok Nallagalva
finally :/
2014-09-16 16:04:05 do_do
AC in one go... can be solved using three variables.. :)my first dp
2014-09-07 14:54:27 mayank
Did, memoization first, then reduced it to 3 variables. My first DP :)
2014-09-01 15:38:47 Dhruv Mullick
Managing 0 is the tricky part.
2014-08-28 20:26:15 Anubhav Balodhi
just did it ^_^
2014-08-26 10:07:21 Vaibhav Gosain
my first memoization!!!
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