[Math] Recurrence of T(n) = T(n/3) + T(2n/3)

recurrence-relations

I've searched online for this but I only seem to find answers for a similar equation:

T(n) = T(n/3) + T(2n/3) + cn

But the one I'm trying to solve is:

T(n) = T(n/3) + T(2n/3)

Base case: We can assume T(a) = Theta(1) for any constant a.

I've succeeded in proving (by induction) that T(n) = O(n*log(n)). I thought the answer should be Theta(n*log(n)), but I cannot prove that T(n) = Omega(n*log(n)).

So my question is – am I correct that the answer is O(n*log(n)), and NOT Theta(n*log(n))? IF that's true that would really be great…

If I'm wrong I will of course explain where I'm stuck in the induction process…

Thanks!

P.S. If you need to, please try to explain using induction, because I haven't learned all methods for solving these problems yet.

Best Answer

umm, if you have solution for $cn$ take $c=0$? Why waste time?

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