programming-for-dummies

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Taking Action on Trees
1. Traverse the left sub-tree using in-order.
2. Visit the root node.
3. Traverse the right sub-tree by using in-order.
Postorder traversal
Postorder traversal traverses the left and right sub-trees first and then visits
the root node, as follows:
1. Traverse the left sub-tree in postorder.
2. Traverse the right sub-tree in postorder.
3. Visit the root node.
Level order traversal
Level order traversal starts at the top level of a tree and traverses the row of
nodes on the same level from left to right. Then it drops to the next lower
level and repeats the process all over again.
When writing actual code to traverse a tree, it’s often easier to write a recursive
subprogram that calls itself and traverses a successively smaller part of
the tree (sub-tree) until it finally stops.
Adding new data
Adding data to a linear structure, like a collection or a stack, is straightforward
because the data structure simply gets bigger. Adding data to a tree is
slightly more complicated because you can add new data at the end of a tree
(on one of its leaf nodes) or anywhere in the middle of the tree.
In an unordered tree, you can insert data anywhere, but in an ordered binary
tree, inserting new data means sorting the data at the same time, as shown
in Figure 5-12.
The order that you store data determines the position of that data in a tree
because newly added data gets added based on the existing data’s values.
Deleting data
Deleting data from a tree can cause special problems because after deleting
data, you may need to rearrange any nodes that were underneath the
deleted data, as shown in Figure 5-13.