ABCD  Colours A, B, C, D
Consider a table with 2 rows and 2N columns (a total of 4N cells). Each cell of the first row is coloured by one of the colours A, B, C, D such that there are no two adjacent cells of the same colour. You have to colour the second row using colours A, B, C, D such that:
 There are exactly N cells of each colour (A, B, C and D) in the table.
 There are no two adjacent cells of the same colour. (Adjacent cells share a vertical or a horizontal side.)
It is guaranteed that the solution, not necessarily unique, will always exist.
Input
[a natural number N ≤ 50000]
[a string of 2N letters from the set {A, B, C, D}, representing the first row of the table]
Output
[a string of 2N letters from the set {A, B, C, D}, representing the second row of the table]
Example
Input: 1 CB Output: AD
Input: 2 ABAD Output: BCDC
hide comments
candide:
20170411 12:41:30
Accurate problem description. Solution needs much more tricky logic than algorithmics. Keep it simple! remember: you have 4 colors and each row has even length ... 

Pratik Ritesh:
20170321 15:21:48
really nice problem..try breaking down to subproblem (keep in mind length of given row is even)..:)


stark_attack:
20170217 08:23:35
getting WA answer after 18th testcase any suggestions . 

vivek4434:
20170130 21:10:37
what is meant by first condition ??


papan_97:
20161216 18:16:04
Tried again after a long time...this time AC in second go after a stupid runtime error i made. Even after getting AC i couldn't believe it was so simple .. :p


sanjay:
20160602 08:58:42
Took a long time to get AC 

rayofhopee:
20160520 16:34:58
If stuck at testcase 9.....try this..


comp0zr:
20160508 04:52:11
Two compilation errors because I forgot to remove a few isolated references to a debugging macro I added, but after I did that I got and AC on my first scored submission (which at this point in my development as a programmer is quite an accomplishment!). Like usual, I spent all night coming up with a convoluted algorithm that included multidimensional arrays and random number generation, but eventually gave up and realized while I was out for the day how simple the solution for this actually is! Completely trashed my original approach and ended up finishing it in about 2 hours... like welldesigned algorithms so often seem to be, the best approaches are often much simpler than they first appear. In any case, this site is great, I can see an immense improvement in my understanding of many concepts since I've been here. Cheers! 

poojan :
20160309 14:36:18
2 WA ans But Finally Got It Awsome Que! One wa bcs Not terminate string '\0':


enigmus:
20160224 15:19:52
Hint: Try building up your solution from smaller pieces 
Added by:  Adrian Satja Kurdija 
Date:  20110313 
Time limit:  0.190s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 GOSU 
Resource:  inspired by a math puzzle 