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
ummihopes: 2020-08-10 07:36:56

I m getting wrong answer on submit when i try with Python? What to do? Only we need to try with C++?

eycer1: 2020-07-30 21:02:07

Take care whith cases '0' containing. 0's are allowed to be in the cases : )

kishor_e: 2020-07-29 15:54:23

Where are the AC in one go guys? lol

Simes: 2020-07-17 11:32:57

Hey @stark_mark1: did you miss this "All answers will be within the range of a 64 bit signed integer."

Last edit: 2020-07-17 11:33:08
stark_mark1: 2020-07-16 20:26:41

don't solve this using python.....python doesn't have integer overflow....and the problem counts on this....
For example in python: '1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111'
output is 1454489111232772683678306641953
while in c++ its : -1674205151.
The setter doesn't account for this....:-(
Some modulus should have been put in.

mm21: 2020-07-16 18:50:38

Ah, thanks for the people who helped with test cases. The problem doesn't specifies for cases like 03 or 04 which are invalid cases. So when they occur in numbers like 104 then we have only 1 correct combination: 10 and 4, it cannot be 1 and 04.

Last edit: 2020-07-16 18:51:01
rishabh_0100: 2020-07-15 12:33:41

answer for some of the test cases:
1010 ->1

shivamvermadev: 2020-07-12 17:42:35

Solved in 2nd Attempt.

abhishekv18: 2020-07-03 07:48:36


Last edit: 2020-07-03 08:46:10
jalotra: 2020-05-19 04:49:53

This was not a good question, the boundary cases I got to know from the comments. So please check the comments. Also see my submission for more clarity :

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