# How to find all sub arrays from an array in o(n) complexity?

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How to find all sub arrays from an array in o(n) complexity?
posted May 5, 2014
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I don't think it is possible since a given array has n* (n+1)/2 subarrays.So it's inherent complexity is O(n^2). Is it possible to find all permutations of a string in complexity less than O(n!)  :)... Also is it possible to find all combination of a group of items in complexity less than O(2^n).
I also have the similar understanding that finding all subarray of an array can not be achieved in o(n) time. Would you like to clarify further?
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+1 vote

Say you are given

``````int a[ ] = {1,2,3,4};
int b[ ] = {4,3,2,1};
int S = 5;
``````

Now the task is to find all pairs of two number which adds up to S (One number from a and other number from b).

+1 vote

While reading possible time complexity i found that time complexity O(log log n) exist for some algos,

Can any one explain an example which shows the calculation of the time complexity with O(log log n)