ACODE - Alphacode

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.






hide comments
problem_solved: 2019-01-29 15:06:07

1101 should be 1

bufftowel: 2019-01-26 14:31:52

Guys though it is not mentioned in the question but we actually need to output 0 in an invalid case. A lot of people mentioned that they got AC without taking care of this , but well in my case that did not work, so if you are having any problem then try putting zero as output in case of invalid input.

chirag7145: 2019-01-20 09:03:25

If our input is like 30 or 300 or 200 what will be the output for these conditions

Last edit: 2019-01-20 09:06:39
its_ulure: 2019-01-02 14:26:15

" All answers will be within the range of a 64 bit signed integer." ---- > This is not guaranteed at all , as there may be weak test cases as for "1111.... (5000 times)" for which the answer does not fits into 64 bit integer

Last edit: 2019-01-02 14:26:48
whyamievenhere: 2018-12-30 09:33:07

Last edit: 2018-12-30 09:36:35
magetron: 2018-12-29 17:53:15

110 is interpreted to 1 10 -> AJ

infinite048: 2018-12-20 20:36:23

thanks for providing corner cases <3

anshumanc007: 2018-12-17 00:00:02

just keep in mind cases with zero in between !

Last edit: 2018-12-17 00:00:40
Asokan R: 2018-12-16 21:00:15

Thanks for the test cases!!

amanharitsh: 2018-12-15 14:26:25

110 is 1
while 260 is 0 why ? , if 110 can be interpreted as 11 mapped to K then why not 26 to Z?

Added by:Adrian Kuegel
Time limit:0.5s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Resource:ACM East Central North America Regional Programming Contest 2004