WSCIPHER - Ws Cipher

Weird Wally's Wireless Widgets, Inc. manufactures an eclectic assortment of small, wireless, network capable devices, ranging from dog collars, to pencils, to fishing bobbers. All these devices have very small memories. Encryption algorithms like Rijndael, the candidate for the Advanced Encryption Standard (AES) are demonstrably secure but they don't fit in such a tiny memory. In order to provide some security for transmissions to and from the devices, WWWW uses the following algorithm, which you are to implement.

Encrypting a message requires three integer keys, k1, k2, and k3. The letters [a-i] form one group, [j-r] a second group, and everything else ([s-z] and underscore) the third group. Within each group the letters are rotated left by ki positions in the message. Each group is rotated independently of the other two. Decrypting the message means doing a right rotation by ki positions within each group.

Consider the message the_quick_brown_fox encrypted with ki values of 2, 3 and 1. The encrypted string is _icuo_bfnwhoq_kxert. The figure below shows the decrypting right rotations for one character in each of the three character groups.

Looking at all the letters in the group [a-i] we see {i,c,b,f,h,e} appear at positions {2,3,7,8,11,17} within the encrypted message. After a right rotation of k1=2, these positions contain the letters {h,e,i,c,b,f}. The table below shows the intermediate strings that come from doing all the rotations in the first group, then all rotations in the second group, then all the rotations in the third group. Rotating letters in one group will not change any letters in any of the other groups.

[a-i], k1= 2 [j-r], k2= 3 [s-z] and _, k3= 1
Encrypted: _icuo_bfnwhoq_kxert _heuo_icnwboq_kxfrt _heuq_ickwbro_nxfot
Decrypted: _heuo_icnwboq_kxfrt _heuq_ickwbro_nxfot the_quick_brown_fox
 ^^   ^^  ^     ^  
    ^   ^  ^^ ^  ^  
^  ^ ^   ^   ^ ^  ^  

All input strings contain only lowercase letters and underscores(_). Each string will be at most 80 characters long. The ki are all positive integers in the range 1-100.

Input consists of information for one or more encrypted messages. Each problem begins with one line containing k1, k2, and k3 followed by a line containing the encrypted message. The end of the input is signalled by a line with all key values of 0.

For each encrypted message, the output is a single line containing the decrypted string.

2 3 1
1 1 1
3 7 4
2 4 3
0 0 0

hide comments
maximilian_21: 2016-08-02 22:59:41

AC: in one go, interesting question

razor123: 2016-06-27 13:32:36

There are few test cases where size of string exceeds 80 characters. Gave me wrong ans when I took MAX as 80 but when I increased it to 85 it got accepted.

fasahat hussain: 2016-06-17 23:17:43

nice implementing..

waelalgaml: 2016-03-06 19:44:01

bla bla bla
-_- -_- -_-

Aswin Siva: 2016-01-16 18:26:48

the_quick_brown_fox => _icuo_bfnwhoq_kxert | using (2, 3, 1) [a-i] [j-r] [s-z _] |
Shouldn't this be encrypted as "sf..."
Can someone please explain what is left rotation in a group ? Isn't it the case where the character is replaced by k_i_th character to the left (with wrap-around) in the same group ?

Last edit: 2016-01-16 18:28:27
(Tjandra Satria Gunawan)(曾毅昆): 2015-08-27 22:02:07

I'm sure this problem is easy, but SIGFPE is really unexpected :p

anuveshkothari: 2015-07-19 07:23:36

Last edit: 2015-07-19 07:31:54
Nitesh Tiwari: 2015-06-14 21:15:48

Finally, after 3 SIGSEGV and 1 SIGFPE.
Remember If the size of the group is zero, then no point considering any value of K(i), take K(i) as zero,else If value of K(i) is greater than that group size, take the modules, K(i)%group.size().

i_am_looser: 2015-06-08 07:54:21

For me , it was easy to implement ;)

Last edit: 2015-06-08 07:54:56
Shubham Mohanka: 2014-10-16 13:19:54

can somebody give me a few corner cases

Added by:Wanderley Guimarăes
Time limit:0.194s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:ACM Mid Central Regionals 2001