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
askdjfn: 2018-06-09 23:11:00

cin works fine

a_ranjan: 2018-06-01 21:05:51

@Austin Lasher if input is 2002 then answer should be zero,why your code does not satisfies these properties??

ankur314: 2018-05-31 15:33:12

If you are getting WA check for

theabd123: 2018-05-25 09:49:39

mostly similar to printing Nth term of Fibonacci series.

nitish235: 2018-05-10 19:55:12

i was getting WA because i was printing two time when size of string becomes 1.check these things also :|

sai: 2018-04-25 08:31:33

OK, folks. I'm using recursion with memoization. It still gives time limit exceeded. What do I do? Python 2.7

Last edit: 2018-04-25 08:38:36
Austin Lasher: 2018-04-21 04:22:16

Great problem. A few comments here suggest to keep track of invalid inputs like "2002", but this is not true as the problem input explicitly says the input will be properly formatted. I submitted a solution that assumes input to be valid (and returns non-zero for "2002") and got AC.

coding_panda: 2018-04-02 13:14:45

Top-Down dp works, use a global array to store solutions. Be careful with 0's !

arnabfromjec05: 2018-03-19 17:41:36

why does both top down as well as bottom up soln is giving wrong ans. even though all the sample test cases are are correct ?? can someone please help!!

yaswanth desu: 2018-03-17 07:25:41

As per question, we should display all possible combinations but if we do like that WA is coming.
For e.g., 20202
here it can be decoded as 20-20-2 , 2-020-2, 2-02-02 which are also a valid ones.
but the accepted answers ares 20-20-2
Any thing with starting 0 is not being considered.
Shouldn't we consider.

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