Binary Tree and its recursive traversal

Binary tree traversal

1. Application of the binary tree, it is often required to find the node in the tree with certain features or nodes of the tree one by one subjected to a treatment, this presents a problem of how to traverse the binary tree.
2. We want to visit each node in the tree according to a path search section, and that each node has, and is accessed only once . "Access" means a lot, may be a node for various processes, such as the output node information and the like. Linear traversal of the structure is easy to solve a problem, and for the binary tree is not the case, since the binary tree is a nonlinear structure, each node of which may have 0-2 subtrees, and therefore a need for a law, so that the nodes can be arranged on the binary tree on line queue to facilitate traversal.
3. If we require to traverse here first left and right, then only three cases, namely root around, left and right root, root around, we are referred to preorder, preorder, postorder.
4. The picture shows the two following two examples, and the results are given in the first order, in sequence, after traversal of:
   
   
5. Here preorder, inorder, postorder recursive way I used to go to achieve, move in sequence as an example, the core code is the root of the left-right ideological :()

void inOrder(BiTree& T)
{
	if(T)
	{
		inOrder(T->lchild);
		visit(T->data);
		inOrder(T->rchild);
	}
}

7. Here is a complete binary tree traversal implementation code:

#include <iostream>
#include <cstdio>
#include <cstdlib>

using namespace std;

//二叉链表的结点结构 
typedef struct BiTreeNode{
	char data; 					//数据域 
	struct BiTreeNode* lchild;  //左孩子指针域 
	struct BiTreeNode* rchild;  //右孩子指针域 
}BiNode,*BiTree;

void CreateBiTree(BiTree& T);	//初始化添加二叉树信息 
void preOrder(BiTree& T);  		//先序遍历二叉树:根 左 右 
void inOrder(BiTree& T);  		//中序遍历二叉树:左 根 右 
void postOrder(BiTree& T);  	//后序遍历二叉树:左 右 根 

void CreateBiTree(BiTree& T)
{
	char ch;
	cin>>ch;
	if(ch=='#')	T=NULL;
	else
	{
		if(!(T=(BiNode*)malloc(sizeof(BiNode))))  exit(0);
		T->data=ch;
		//这里注意正确输入的顺序 
		CreateBiTree(T->lchild); //先构造左子树 
		CreateBiTree(T->rchild); //再构造右子树 
	}
}

int visit(char data1)
{
	cout<<data1;
	return 0;
}

void preOrder(BiTree& T)
{
	if(T)
	{
		visit(T->data);
		preOrder(T->lchild);
		preOrder(T->rchild);
	}
}

void inOrder(BiTree& T)
{
	if(T)
	{
		inOrder(T->lchild);
		visit(T->data);
		inOrder(T->rchild);
	}
}

void postOrder(BiTree& T)
{
	if(T)
	{
		postOrder(T->lchild);
		postOrder(T->rchild);
		visit(T->data);
	}
}

int main()
{
	//测试用例：
	//ABE##F##C#DG###
	//-+a##*b##-c##d##/e##f##
	BiTree T;
	CreateBiTree(T);
	preOrder(T);
	cout<<endl;
	inOrder(T);
	cout<<endl;
	postOrder(T);
	return 0;
} 

Results are as follows: