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
kunal1996: 2016-02-11 10:47:16

is 200202 a valid input

Rajat Jain: 2016-01-30 08:04:17

Nice question.. take care of 0 in input... DP.. AC..

mohd_sharique: 2016-01-28 15:28:52

I dont get the reason as to why 101 will give output as 1. Can't it have two possible ans: JA{10,1} and AA{1,01} ?

chandan kumar: 2016-01-27 14:44:12

got ac in 2nd time. it's great feeling for beginner like me :)
No need of memoization.Take care of 0 in i/p.

try2catch: 2016-01-22 12:35:12

finally understood....single shot AC !

praby: 2016-01-18 16:26:47

For the people getting WA pls take care of numbers with 0's between them.
i.e. 101 : 1
11101: 2

rayofhopee: 2016-01-16 03:59:08

nice question ....just take care of 0

nitin jain: 2016-01-12 20:37:53

just think some tricky cases and got ac !!

dwij28: 2016-01-05 16:43:23

Feels great to get AC in this at one go. Finally, I am learning DP. :D

karthik1997: 2015-12-28 18:08:17

There wont be any invalid input like 1000 ( consecutive zeroes of any size) . Just one zero is possible in between
Follow every test case mentioned in comments ,They will help you a lot .
For 01 , 02 , 09 -- output -0

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