 Am i the only one who couldn’t solve any problem Frustrated.

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Beleive me you are not. Problem set was harder than last years without any cakewalk problem!

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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 2-3 hours trying euclid’s method and what not , to no avail !

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Well, you want to solve Nx+d*(N-1)*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:

1. R*C = M + K + J
2. One piece should have one of the dimension as R or C (think about it)
3. 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.

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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:

1. VCAKE: only 2 possible cake cuts: make cases.

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

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

4. RWALK: subset sum - hit nearest to sum/2.

The above 4 were not more than 20 lines.

1. SEGSUMQ - simple range sum query on persistent segtree(tedious to code)

Though I did not solve NUMSET, it should be doable by max-flow or some MIS algorithm for such special graphs.

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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.

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