What is time complexity of this algorithm?

Question

Suppose we have an array w, that contains n integers. By the following definition, and the following pseudo code, please, tell me what is the time complexity of the algorithm w.r.t. n:

idx[i] = max(j) : 1 <= j < i and w[j] < w[i]

alg:
Data: w : array of integers - idx: a pointer to maximum index with the less value.
Date: w is 1based

idx[1] = -1
for i=: 2 to n do
  j=i-1
  while w[j] > w[i] and j <> -1
  {
    j = idx[j]
  }
  idx[i] =j
end

Srikar Appalaraju · Accepted Answer · 2013-02-23 13:43:34Z

1

You have 2 loops here -

First loop for loop runs n times. hence its O(n).
Second loop while loop runs each time from (i-1) + (i-2) + (i-3) + .... + (i-n). it runs for (n-1) times. So O(n).

Combines to O(n^2) algo. The other operations are either constant time or O(n) time, hence neglected.

answered Feb 23, 2013 at 13:43

Srikar Appalaraju

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