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ACODE - Alphacode

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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
xceptor: 2015-09-02 16:25:18

easy one, just take care about '0'

Satish: 2015-08-27 21:35:05

Am i a fool ? Not able to solve even after 5 hours :(

rakhejabhai: 2015-08-26 08:00:07

Consider the test case

The answer is 1

Mohit: 2015-08-24 17:22:38

got ac in 3rd attempt....
when i follow some test cases in comments...

Hitesh Saini: 2015-08-21 10:38:33

finally accepted (Y)
recursion, memoization

Last edit: 2015-08-21 10:39:08
coder_shishir: 2015-08-19 08:52:21

messed up ....but finally solved.....
few more cases:
output :

suhas: 2015-08-16 20:40:52

Nice problem... love DP :) but got help from the extra test cases provided here. Thanks

Babu: 2015-08-13 17:42:52

The testcases contain no invalid output.chill

Last edit: 2015-08-13 17:43:48
einsdurchnull: 2015-08-06 04:10:04

Eeeh, solved it on the first try with a fibonacci table and without DP?! Is that weird, or someone did it the same?

anuveshkothari: 2015-08-01 13:18:04

finally AC...
after lots of WA..