title: Are there any problems that can only be solved recursively or only iteratively?
body: <p>Is there any problem that can only be solved in recursion or iteration. If not, can all algorithms be represented in either form having the same complexity?</p>
  
  <p><strong>PS:</strong> I'm talking about the theoretical complexity(O, theta and omega) and not about the time taken when implemented in real world systems.</p>