线索二叉树（后序）

最新推荐文章于 2025-12-07 17:05:22 发布

原创最新推荐文章于 2025-12-07 17:05:22 发布 · 73 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#c语言 #开发语言

文章介绍了如何用C语言定义和操作二叉树结构，包括创建树节点、后序遍历以及获取前驱节点的方法。主要展示了`create`、`postthread`和`GetFirst/GetNext`等关键函数。

#include <stdio.h>
#include <stdlib.h>

typedef struct TREE {
	char data;
	struct TREE* Lchild;
	struct TREE* Rchild;
	struct TREE* Parent;
	int rtag;
	int ltag;
}TREE,*PTREE;

void create(TREE** T,PTREE parent) {
	char data;
	scanf("%c", &data);
	getchar();
	if (data != '#') {
		*T = (PTREE)malloc(sizeof(TREE));
		(*T)->data = data;
		(*T)->ltag = 0;
		(*T)->rtag = 0;
		(*T)->Parent = parent;
		create(&(*T)->Lchild,*T);
		create(&(*T)->Rchild,*T);
	}
	else
	{
		*T = NULL;
	}
}

void postthread(PTREE T, TREE** pre) {
	if (T) {
		postthread(T->Lchild, pre);
		postthread(T->Rchild, pre);
		if (T->Lchild == NULL) {
			T->ltag = 1;
			T->Lchild = *pre;
		}
		if (*pre != NULL && (*pre)->Rchild == NULL) {
			(*pre)->rtag = 1;
			(*pre)->Rchild = T;
		}
		*pre = T;
	}
}

PTREE GetFirst(PTREE T) {
	while (T->ltag == 0) {
		T = T->Lchild;
	}
	if (T->rtag == 0) {
		return GetFirst(T->Rchild);
	}
	else
	{
		return T;
	}
}

PTREE GetNext(PTREE node) {
	if (node->rtag == 1) {
		return node->Rchild;
	}
	else
	{
		if (node->Parent == NULL) {
			return NULL;
		}
		else if (node->Parent->Rchild == node) {
			return node->Parent;
		}
		else
		{
			if (node->Parent->rtag == 0) {
				return GetFirst(node->Parent->Rchild);
			}
			else
			{
				return node->Parent;
			}
		}
	}
}

int main() {
	PTREE T;
	create(&T,NULL);
	PTREE pre = NULL;
	postthread(T, &pre);
	for (PTREE node = GetFirst(T); node != NULL; node = GetNext(node)) {
		printf("%c", node->data);
	}
	return 0;
}