Efficient algorithm for printing sub-arrays

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I need an efficient algorithm for printing all sub-arrays of an array.
By sub-arrays I mean contiguous subsequences of an array.

What I have tried:

The algorithm available on the web uses three nested for loops with
time complexity O(n^3), which is not at all efficient. Is there a better algorithm which can print all sub-arrays in quadratic or linear time? I l know that time complexity is not determined by the number of loops.

Posted 15-Jun-22 1:34am

Vaibhav Vishal Singh

Updated 15-Jun-22 2:07am

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Comments

Richard Deeming 15-Jun-22 7:44am

For a single-dimensional array, why would you need more than two loops? (One for the start index, and one for the length.)

Vaibhav Vishal Singh 15-Jun-22 7:50am

I need all sub-arrays (1<=length of sub-array<=length of array)

CPallini 15-Jun-22 8:01am

You forgot the loop needed to print the sequence.

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CPallini · Answer 1 · 2022-06-15T02:07:00

Solution 1

This implements the algorithm suggested by Richard.
Still, it is O(N^3).

C++

void show_subarrays( int a[], int N)
{
  for (int l=1; l<=N; ++l)
  {
    int k = 0;
    while ( (k+l) <= N)
    {
      for (int j=0; j<l; ++j)
        cout << a[k+j] << " ";
      cout << "\n";
      ++k;
    }
  }
}

Posted 15-Jun-22 2:07am

CPallini

Comments

merano99 15-Jun-22 12:00pm

Isnt this a for loop?
int k = 0;
while ( (k+l) <= N) { ... k++;}

for(k=0; (k+l) <= N; k++){..}

CPallini 16-Jun-22 2:52am

Yes, it is.