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
aashish_a2z: 2018-12-09 21:48:22

First of all don't worry about the invalid strings.....Take care only for valid strings
Take case for the string length equal to 1 too...
Check for the following test cases:
1020 --> 1
1101 --> 1
110 --> 1
All the Best :)

Last edit: 2018-12-09 21:48:53
Prasanna: 2018-12-02 16:47:00

Test all these combinations:(which includes all boundary cases)

nacholibre: 2018-11-19 18:46:06

919 -> 2

me_milan_11: 2018-10-07 11:00:29

finally, AC :) handle cases which contains '10' and '20' in it. That is the tricky part. Don't bother about invalid test cases. There are no such cases. Every time answer would be > 0

masterchef2209: 2018-10-05 11:44:01

i was improving my solution according to test cases and it got accepted but i still can't understand how is my ugly code correct lol

andrew_belkin: 2018-09-21 10:18:09

Thank you colleagues for all the test cases!

amiratou: 2018-09-19 22:10:12

Easy Peasy !

mayank_75: 2018-09-02 23:01:15

Last edit: 2018-09-02 23:05:09
san__123: 2018-09-02 10:28:06

be careful with 0's in the input like 1101,
done in c++ :)

starry91: 2018-08-15 18:43:34

how can 0 occur in the input as chars start from 1-26??

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