For constants \(a≥1\) and \(b>1\), consider the following recurrence defined…

GATE · 2021 · CS · Set 2 · Computer Science & IT

For constants a≥1a≥1 and b>1b>1, consider the following recurrence defined on the non-negative integers:

T(n)=a⋅T(nb)+f(n)T(n) = a \cdot T \left(\dfrac{n}{b} \right) + f(n)

Which one of the following options is correct about the recurrence T(n)T(n) ?

  1. A.

     if f(n)f(n) is nlog⁡2(n)n \log_2(n) , then T(n)T(n) is Θ(nlog⁡2(n))\Theta(n \log_2(n)) .

  2. B.

    if f(n)f(n) is nlog⁡2(n)\dfrac{n}{\log_2(n)} , then T(n)T(n) is Θ(log⁡2(n))\Theta(\log_2(n)) .

  3. C.

     if f(n)f(n) is O(nlog⁡b(a)−ϵ)O(n^{\log_b(a)-\epsilon}) for some ϵ>0\epsilon >0, then T(n)T(n) is Θ(nlog⁡b(a))\Theta(n^{\log_b(a)}) .

  4. D.

     if f(n)f(n) is Θ(nlog⁡b(a))\Theta(n^{\log_b(a)}), then T(n)T(n) is Θ(nlog⁡b(a))\Theta(n^{\log_b(a)}) .

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