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
suaeb_ahmed: 2021-10-01 20:09:32

check this input:

kennedy777: 2021-09-30 22:01:03

This problem has a weak testcase, My code solves string "27" = 2 and the correct solution is 1, but it is accepted.

tusharsingh432: 2021-07-27 07:04:38

I tried like a 100 times and the soln works everywhere else but this question just won't take it

parasnagpal: 2021-07-15 11:41:40

Check out this video tutorial:

Last edit: 2021-07-15 12:39:55
kundan2000: 2021-06-09 19:29:35

Nothing to do with 0 simply check if current character is '0' simply ignore all of its further branches in the recursion tree.

hemraj_07: 2021-05-30 07:42:10

Edge case: Check if the given digit is zero or not and do accordingly.

harshh3010: 2021-01-31 20:18:14

Result for inputs like 10001 will be 0

iwandepe: 2021-01-24 09:24:30

if you still confuse how to solve this problem. try to think about fibonacci sequence. then handle the case with '0' values

subhamhimself: 2021-01-11 19:21:14


ritik042: 2021-01-11 15:35:42


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