Tree is iterated by using `Level-order Traversal Algorithm" In level-order traversal we iterating nodes level by level, starting from root, and going deeper and deeper in tree.
Tree is iterated by using `Post-order Traversal Algorithm" In post-order traversal, we starting from most left child. First visit all children of parent, then parent.
Tree is iterated by using `Pre-order Traversal Algorithm" The pre-order traversal is a topologically sorted one, because a parent node is processed before any of its child nodes is done.