Question:

Consider the following functions, where \(n\) is a positive integer.
\[ n^{1/3}, \quad \log(n), \quad \log(n!), \quad 2^{\log(n)} \]
Which one of the following options lists the functions in increasing order of asymptotic growth rate?
Note: Assume the base of log to be 2.

Show Hint

Simplify $2^{\log n}$ to $n$ first, recall $\log(n!)$ grows like $n\log n$, and remember any positive power of $n$ eventually beats any power of $\log n$.
Updated On: Jul 22, 2026
  • \( \log(n), \; n^{1/3}, \; 2^{\log(n)}, \; \log(n!) \)
  • \( n^{1/3}, \; \log(n), \; \log(n!), \; 2^{\log(n)} \)
  • \( \log(n), \; n^{1/3}, \; \log(n!), \; 2^{\log(n)} \)
  • \( 2^{\log(n)}, \; n^{1/3}, \; \log(n), \; \log(n!) \)
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is A

Solution and Explanation

Step 1: Simplify \(2^{\log(n)}\) since log is base 2.
By definition, \(2^{\log_2(n)} = n\). So this function is really just \(n\), growing linearly.

Step 2: Recall the growth rate of \(\log(n!)\) using Stirling's approximation.
By Stirling's approximation, \(n! \approx \sqrt{2\pi n}\,(n/e)^n\), so
\[ \log(n!) \approx n\log(n) - n\log(e) + \frac{1}{2}\log(2\pi n) \]
The dominant term is \(n\log(n)\), so \(\log(n!)\) grows like \(n\log(n)\), which is strictly faster than plain linear growth \(n\), and faster than everything else in the list, once \(n\) is large.

Step 3: Compare the remaining two functions, \(\log(n)\) and \(n^{1/3}\).
It is a standard asymptotic fact that any positive power of \(n\) eventually grows faster than any power of \(\log(n)\); in particular \(n^{1/3}\), a polynomial growth rate, eventually overtakes \(\log(n)\), a much slower logarithmic rate, even though \(\log(n)\) might look bigger for very small n. As \(n \to \infty\), \(\dfrac{\log(n)}{n^{1/3}} \to 0\), confirming \(\log(n) = o(n^{1/3})\). So \(\log(n)\) grows slower than \(n^{1/3}\).

Step 4: Put all four functions in increasing order of growth rate.
Slowest: \(\log(n)\).
Next: \(n^{1/3}\), since a polynomial beats a logarithm.
Next: \(2^{\log(n)} = n\), since a full linear power beats a fractional power like \(n^{1/3}\) (exponent 1 is bigger than 1/3).
Fastest: \(\log(n!) \approx n\log(n)\), since an extra factor of \(\log(n)\) on top of linear beats plain linear \(n\).
So the increasing order is:
\[ \log(n) \;<\; n^{1/3} \;<\; 2^{\log(n)} \;<\; \log(n!) \]

Step 5: Match with the options and rule out the others.
Option (A) lists exactly \(\log(n), n^{1/3}, 2^{\log(n)}, \log(n!)\), matching Step 4. Option (B) puts \(n^{1/3}\) before \(\log(n)\), which is backwards. Option (C) puts \(\log(n!)\) before \(2^{\log(n)}\), which is backwards since \(n\log(n)\) grows faster than \(n\). Option (D) starts with \(2^{\log(n)}=n\), which is wrong since \(n\) grows faster than both \(\log(n)\) and \(n^{1/3}\), so it cannot be first.

Final Answer:
The increasing order of growth is \(\log(n), n^{1/3}, 2^{\log(n)}, \log(n!)\). \[ \boxed{\text{Option (A)}} \]
Was this answer helpful?
0
0

Top GATE CS Algorithms Questions

View More Questions