For example, for A normal full node in the figure above, A is the root node, B is the left node, and C is the right node. The preceding order is ABC (the root node comes first, and then the left node comes first and then the right node at the same level). The middle order is BAC(first left, then root, and finally right); The trailing order is BCA (first left, then right, and last root).
Take the binary tree traversal result above
Preceding traversal: ABCDEFGHK
Middle order traversal: BDCAEHGKF
Sequential traversal: DCBHKGFEA
Order traversal in analysis is shown in the following figure. Middle order is more important.
