Ciro Santilli This is a bit harder than iterative pre-order: now we have to check if there is a left or right element or not:
- (START) push current
- if there is left:
- move left
- else:
- (ELSE) pop
- visit
- if there is right
- move right
- GOTO START
- else:
- GOTO ELSE
The control flow can be slightly simplified if we allow NULLs: www.geeksforgeeks.org/inorder-tree-traversal-without-recursion/