Am i the only one who couldn’t solve any problem
Frustrated.
Beleive me you are not. Problem set was harder than last years without any cakewalk problem!
I solved one in 26 mins, then it took me 21 wrong tries. And it was like, “What am I doing with my life!”
And the 21 went in vain.
I think problems weren’t hard this time but a lot trickier, even though I could solve only 2 problems (VCAKE and COLTREE) , in COLTREE only n and k were required and not the structure of the tree.
I think solutions of first 4 problems won’t be more than 10 lines of code.
IMO, it was easier than last year, first 2 problems were really trivial.
I think problems weren’t hard this time but a lot trickier, even though I could solve only 2 problems (VCAKE and COLTREE) , in COLTREE only n and k were required and not the structure of the tree.
I think solutions of first 4 problems won’t be more than 10 lines of code.
Can you please explain 2nd problem, could not get it even now, what I understood was, you are given sum of A.P and number of terms in the A.P and you want to know whether a positive integer A.P exists or not with such property.
Did anyone solve the second question , “Chocolate for Everyone” ?
Spent 23 hours trying euclid’s method and what not , to no avail !
Well, you want to solve Nx+d*(N1)*N/2 = C where x and d >=1, u have 2 cases if N is even or odd
Could you describe the approach for VCAKE plz?
can any one tell me how you solved 2nd one ? I formed the equation in ax+bx=c after that I used the condition
if(c% gcd(a%b) ) is true then yes …
Initially I subtracted n*(n+1)/2 from C to ensure that each get atleast one with common difference>=1. But still got WA. Dont know why
You must agree that following conditions should hold:
 R*C = M + K + J
 One piece should have one of the dimension as R or C (think about it)
 Then you are left with a reduced cake with dimensions (X) * (X’  Z/X), (X = R or C, X’ = C or R, Z = M or K or J, resp.), then apply same process as in 1 and 2 for 2 pieces.
My solution link : http://ideone.com/5TGjIZ
right, couldn’t proceed further or had some bugs in my code, could you please share your code.
I guess we’d have to wait till they publish the editorials. The submissions aren’t public as yet.
try this
4 8
Thanks. About COLTREE i implemented nCr and factorial discarding tree structure but I got WA. What was your approach?
For second one you need to make sure that the solution to ax + by = c has positive values for a and b. You can solve that by modifying the linear diophantine.
The problems were easier than last year’s:
I solved the following:

VCAKE: only 2 possible cake cuts: make cases.

ARITHM: see equation of sum and cases on whether n is odd or even.

COLTREE: no tree required: just f(n,k) simple DP.

RWALK: subset sum  hit nearest to sum/2.
The above 4 were not more than 20 lines.
 SEGSUMQ  simple range sum query on persistent segtree(tedious to code)
Though I did not solve NUMSET, it should be doable by maxflow or some MIS algorithm for such special graphs.
What was the approach for the third one ? I skipped that and did the 4th instead as I couldn’t make any progress and eventually had to move on.