title: Comparing 2 Arrays
body: <p>I have 2 arrays a &amp; b with same length n.</p>
  
  <p>I want to compare every element of a with every element of b. The 2 arrays are not sorted. How can I achieve my goal with an algorithm that has a complexity less that O(n^2)? Like O(n) or O(nlogn)?</p>
  
  <p>The ultimate goal is to find a pair of numbers from these arrays such that their difference is the length of the arrays.</p>