ABCD - Colours A, B, C, D

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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.


[a natural number N ≤ 50000]

[a string of 2N letters from the set {A, B, C, D}, representing the first row of the table]


[a string of 2N letters from the set {A, B, C, D}, representing the second row of the table]













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rayofhopee: 2016-05-20 16:34:58

If stuck at testcase 9.....try this..
answer can be :DCBDCB
was a life saver ...finally ac :-)

comp0zr: 2016-05-08 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 multi-dimensional 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 well-designed 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 : 2016-03-09 14:36:18

2 WA ans But Finally Got It Awsome Que! One wa bcs Not terminate string '\0':
Very Good Que! Must do!

enigmus: 2016-02-24 15:19:52

Hint: Try building up your solution from smaller pieces

Ankit: 2016-02-18 17:23:42

My program runs for a O(n) but still it gives Time Limit Exceeded. Stuck badly. !!

Ankit: 2016-02-17 13:13:54

TLE after 18. The numbers in the bracket, any idea what it means ?

minhthai: 2016-01-15 12:53:12

try to think super simply :)

naruto09: 2015-12-16 20:15:07

WA at 18th test case...can anyone help please..?

darkhire21: 2015-10-18 11:00:37

read carefully statement 1 ..!!!!

(Tjandra Satria Gunawan)(曾毅昆): 2015-08-02 04:25:08

Finally AC, it's hard to think the solution but very easy to implement :)

Added by:Adrian Satja Kurdija
Time limit:0.190s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Resource:inspired by a math puzzle