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Raphael
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Master Method How to the examples for using the master theorem in Cormen $3T( n / 4 ) + n \log n$ and $2T( n / 2 ) + n \log n$work?

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Paresh
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I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = Omega(n^{\log_4(3) + \epsilon})$$f(n) = n\log(n) = \Omega(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $Omega(n^{\log_4(3) + \epsilon})= Omega(n)$$\Omega(n^{\log_4(3) + \epsilon})= \Omega(n)$ so we have $n\log(n) = Omega(n)$$n\log(n) = \Omega(n)$ but it's not true; But he proves that $n\log(n) = Omega( n^{\log_4(3) + \epsilon} )$$n\log(n) = \Omega( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = Omega(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $Omega(n^{\log_4(3) + \epsilon})= Omega(n)$ so we have $n\log(n) = Omega(n)$ but it's not true; But he proves that $n\log(n) = Omega( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = \Omega(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $\Omega(n^{\log_4(3) + \epsilon})= \Omega(n)$ so we have $n\log(n) = \Omega(n)$ but it's not true; But he proves that $n\log(n) = \Omega( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

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I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = O(n^{\log_4(3) + \epsilon})$$f(n) = n\log(n) = Omega(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $O(n^{\log_4(3) + \epsilon})= O(n)$$Omega(n^{\log_4(3) + \epsilon})= Omega(n)$ so we have $n\log(n) = O(n)$$n\log(n) = Omega(n)$ but it's not true; But he proves that $n\log(n) = O( n^{\log_4(3) + \epsilon} )$$n\log(n) = Omega( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = O(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $O(n^{\log_4(3) + \epsilon})= O(n)$ so we have $n\log(n) = O(n)$ but it's not true; But he proves that $n\log(n) = O( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

I'm reading Cormen's Introduction to Algorithms 3rd edition, and in examples of Master Method recursion solving Cormen gives two examples

  1. $3T( \frac{n}{4} ) + n\log(n)$
  2. $2T( \frac{n}{2} ) + n\log(n)$

For the first example we have $a=3$ and $b=4$ so $n^{\log_4 (3)}=n^{0.793}$ and Cormen says that if we choose $\epsilon = 0.207$ then $f(n) = n\log(n) = Omega(n^{\log_4(3) + \epsilon})$

How? As I understand it if $\epsilon = 0.207$ then $Omega(n^{\log_4(3) + \epsilon})= Omega(n)$ so we have $n\log(n) = Omega(n)$ but it's not true; But he proves that $n\log(n) = Omega( n^{\log_4(3) + \epsilon} )$

And then he proves that for the second case $n\log(n)$ does not apply to masters method 3-rd case the same way as I prove above.

So could somebody explain me in detail how the third case of the master's theorem applies to $3T( \frac{n}{4} ) + n \log(n)$ but not to $2T( \frac{n}{2} ) + n\log(n)$.

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Jernej
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AJed
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