快速建立的一种方法：



#include <iostream>
#include <cstdlib>

using namespace std;

#define type char

typedef struct TREE
{
type value;
struct TREE *LSubTree;
struct TREE *RSubTree;
}TreeNode, *PtNode;

PtNode BuildTree()
{

PtNode root;
char ch;
root=new TreeNode;
if(!root)
exit(-1);
cin>>ch;

if(ch=='@')
root=NULL;
else
{
root=new TreeNode;
root->value=ch;

root->LSubTree=BuildTree();
root->RSubTree=BuildTree();
}

return root;

}

void Inorder(PtNode root)
{
if(root!=NULL)
{
Inorder(root->LSubTree);
cout<< root ->value<<endl;
Inorder (root ->RSubTree);
}
}

void Postorder(PtNode root)
{
if(root!=NULL)
{
Inorder( root->LSubTree);

Inorder( root->RSubTree);
cout<< root ->value<<endl;
}
}

/////////////////////////////////////////////
int main()
{
PtNode tree;
cout<<"Test began !\n"
<<"Enter some letters for the tree:(SYMBOL '@' MEANS BLANK)\n";

tree=BuildTree();
Inorder( tree);
Postorder( tree);

return 0;
}

真是很不好意思（哎 复制惹的祸呀）
部分代码修正：
将函数 Postorder(PtNode root)中

Inorder( root->LSubTree);
Inorder( root->RSubTree);
改为：
Postorder(root->LSubTree);
Postorder( root->RSubTree);
另外，在主函数中务必加上：
delete tree;
然后再返回。（OR memorry leak !）