先建立一颗二叉树

实现代码如下：

#include <iostream>
using namespace std;
struct node
{
	int data;
	struct node *L;
	struct node *R;
};
void printnode(struct node *n)//前序遍历
{
	if(n == NULL) return;
	cout << n->data << endl;
	printnode(n->L);
	printnode(n->R);
}
void printnode1(struct node *n)//中序遍历
{
	if(n == NULL) return;
	printnode1(n->L);
	cout << n->data << endl;
	printnode1(n->R);
}
void printnode2(struct node *n)//后序遍历
{
	if(n == NULL) return;
	printnode2(n->R);
	printnode2(n->L);
	cout << n->data << endl;
}
int main()
{
	struct node *n = new struct node;
	n->data = 0;
	n->L = NULL;
	n->R = NULL;
	struct node *n1 = new struct node;
	n1->L = NULL;
	n1->R = NULL;
	n1 -> data = 1;
	n->L = n1;
	struct node *n2 = new struct node;
	n2->L = NULL;
	n2->R = NULL;
	n2->data = 2;
	n->R = n2;
	struct node *n3 = new struct node;
	n3->L = NULL;
	n3->R = NULL;
	n3 -> data = 3;
	n1->L = n3;
	struct node *n4 = new struct node;
	n4->L = NULL;
	n4->R = NULL;
	n4 -> data = 4;
	n1->R = n4;
	printnode2(n);
	system("pause");
	return 0;
}