title: Quadratic algorithm for 4-SUM
body: <p>The 4-SUM is as follows:</p>
  
  <blockquote>
    <p>Given an array of N distinct integers find 4 integers a, b, c, d such that a+b+c+d = 0.</p>
  </blockquote>
  
  <p>I could come up with a cubic algorithm using quadratic algorithm for 3-SUM problem. Can we do better than cubic for 4-SUM?</p>