c++ 树（Tree）的实现

#include<stdio.h>
#include<stdlib.h>
#define M 50
typedef struct Tree {
	int data;
	struct Tree* LChild;
	struct Tree* RChild;
}Tree, * BitTree;

BitTree createTree() {
	int data, t;
	scanf_s("%d", &data);
	t = getchar();
	if (data == -1) { //输入-1表示NULL
		return NULL;
	}
	else {
		BitTree node = (BitTree)malloc(sizeof(Tree));
		node->data = data;
		printf("请输入%d左子树：", data);
		node->LChild = createTree();
		printf("请输入%d右子树：", data);
		node->RChild = createTree();
		return node;
	}
}

//先序、中序、后序递归遍历
void Preorder(BitTree T) {
	if (T == NULL) {
		return;
	}
	printf("%d ", T->data);
	Preorder(T->LChild);
	Preorder(T->RChild);
}
void Inorder(BitTree T) {
	if (T == NULL)
	{
		return;
	}
	Inorder(T->LChild);
	printf("%d ", T->data);
	Inorder(T->RChild);
}
void Postorder(BitTree T) {
	if (T == NULL) {
		return;
	}
	Postorder(T->LChild);
	Postorder(T->RChild);
	printf("%d ", T->data);
}

//层次遍历
void LAYERorder(BitTree T) {
	BitTree Q[M], p;
	int front, rear;
	if (T != NULL) {
		Q[0] = T;//根节点入队头
		front = -1;
		rear = 0;
		while (front < rear) {//rear上升速度大于front
			p = Q[++front];//一次循环输出一次
			printf("%d ", p->data);
			//若三层只要两次就入队完成
			if (p->LChild != NULL) {
				Q[++rear] = p->LChild;
			}
			if (p->RChild != NULL) {
				Q[++rear] = p->RChild;
			}
		}
	}
}

//先序、中序、后序非递归遍历
void PREORDER(BitTree T) {
	BitTree Stack[M], p = T;
	int top = -1;
	if (T != NULL) {
		while (p != NULL || top != -1) {

			while (p != NULL) {//左进
				Stack[++top] = p;
				printf("%d ", p->data);//进栈顺序就是先序遍历顺序
				p = p->LChild;
			}
			p = Stack[top--];//记录当前栈，再退一栈
			p = p->RChild;
		}
	}
}
void INORDER(BitTree T) {
	BitTree Stack[M], p = T;
	int top = -1;
	if (T != NULL) {
		while (p != NULL || top != -1) {
			while (p != NULL) {
				Stack[++top] = p;
				p = p->LChild;
			}
			p = Stack[top--];
			printf("%d ", p->data);
			p = p->RChild;
		}
	}
}
void POSTORDER(BitTree T) {
	BitTree stack1[M], p = T;
	int stack2[M];
	int flag, top = -1;
	if (T != NULL) {
		while (p != NULL || top != -1) {
			while (p != NULL) {
				stack1[++top] = p;
				stack2[top] = 0;//先把节点标记为0
				p = p->LChild;
			}
			p = stack1[top];r
			flag = stack2[top--];//出栈
			if (flag == 0) {
				stack1[++top] = p;
				stack2[top] = 1;//再标记为1，然后到出栈
				p = p->RChild;
			}
			else {
				printf("%d ", p->data);//输出标记为1的节点
				p = NULL;
			}
		}
	}
}