title: How to print a binary tree level by level? Interview question!
body: <p><strong>How to print a binary tree level by level?</strong></p>
  
  <p>This is an interview question I got today. Sure enough, using a BFS style would definitely work. However, the follow up question is: How to print the tree using constant memory? (So no queue can be used)</p>
  
  <p>I thought of converting the binary tree into a linked list somehow but have not come up with a concrete solution.</p>
  
  <p>Any suggestions?</p>
  
  <p>Thanks</p>