Analysis of Algorithm

A Time Complexity Question

A Time Complexity
A Time Complexity Question - Analysis of Algorithm What is the time complexity of following function fun()? Assume that log(x) returns log value in base 2.

What is a time complexity of following function fun()? Assume that log(x) returns log value in base 2.

void fun()
{
   int i, j;
   for (i=1; i<=n; i++)
      for (j=1; j<=log(i); j++)
         printf("GeeksforGeeks");
}

Time Complexity of the above function can be written as Θ(log 1) + Θ(log 2) + Θ(log 3) + . . . . + Θ(log n) which is Θ (log n!)

Order of growth of ‘log n!’ and ‘n log n’ is same for large values of n, i.e., Θ (log n!) = Θ(n log n). So time complexity of fun() is Θ(n log n).

The expression Θ(log n!) = Θ(n log n) can be easily derived from following Stirling’s approximation (or Stirling’s formula).

   log n! = n log n - n + O(log(n)) 
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About the author

Venkatesan Prabu

Venkatesan Prabu

Wikitechy Founder, Author, International Speaker, and Job Consultant. My role as the CEO of Wikitechy, I help businesses build their next generation digital platforms and help with their product innovation and growth strategy. I'm a frequent speaker at tech conferences and events.

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