二叉树是一种重要的非线性数据结构，直观地看，它是数据元素（在树中称为结点）按分支关系组织起来的结构，很象自然界中的树那样。树结构在客观世界中广泛存在，如人类社会的族谱和各种社会组织机构都可用树形象表示。树在计算机领域中也得到广泛应用，如在编译源程序如下时，可用树表示源源程序如下的语法结构。又如在数据库系统中，树型结构也是信息的重要组织形式之一。一切具有层次关系的问题都可用树来描述。满二叉树，完全二叉树，排序二叉树。

　　后序遍历是二叉树遍历的一种。后序遍历指在访问根结点、遍历左子树与遍历右子树三者中，首先遍历左子树，然后遍历右子树，最后遍历访问根结点，在遍历左、右子树时，仍然先遍历左子树，然后遍历右子树，最后遍历根结点。后序遍历有递归算法和非递归算法两种。-Binary tree is an important non-linear data structure, intuitively, it is a data element (called nodes in the tree) organized according to the relationship between branches structure, much like a tree in nature as. Tree structure in the objective world is widespread, such as human society, family tree and a variety of social organizations can be used tree image representation. Tree in the computer field has also been widely used, such as the source code is compiled as follows, the source tree can be used to express the following syntax structure. Another example is in the　system, the tree structure is one of the important forms of information organization. All problems with hierarchical relationships can be described in terms of trees. Full binary tree, complete binary tree, sort binary tree.

Postorder traversal is a kind of binary tree traversal. After traversing the root node, traversing the left subtree and traversing the right subtree, we first traverse the left subtree, and then