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Can we have better solution than O(n^2 log n) for the following problem 1.
By pkpawan, history, 23 months ago, In English

Problem 1 from Past Online assesment of Citadel

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23 months ago, # |
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I am just able to come up with O(n^2 log n). First we will sort the array . We are finding all the pair possible for (i,j) ---> (i<j) such that (A[i] + A[j])<= thresold ,now let the remaining rem = thresold — (A[i] + A[j] ) now if (rem > A[j]), then we will find the larges (value<= rem) in array of remaining elements using binary search and no of valid triplets is (k — j), where 'k' is index of that value.

We will find this for all the valid pairs.

So O(n^2) for valid pairs and for each pair finding the A[k] is (logn). So O(n^2 log n)

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    23 months ago, # ^ |
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    You can achieve $$$O(n^2)$$$ if you replace binary search with two pointers.

    There are no known significantly better upper bounds and the lower bound is widely known open problem. More details here.

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23 months ago, # |
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Just curious, does Citadel hire from India?

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