二叉树的链式结构实现

/*二叉树的链式结构实现
*
*
*/
#include <stdio.h>
#include <stdlib.h>

struct TreeNode;
typedef int ElementType;
typedef char TElementType;
typedef char* String;
typedef struct TreeNode* PtrToNode;
typedef PtrToNode Tree;

String str = "ABDH#K###E##CFI###G#J##";/*前序遍历序列*/
ElementType index = 0;

struct TreeNode{
TElementType data;
Tree LChild;
Tree RChild;
};

Tree CreateBiTree();/*前序遍历法创建一棵二叉树*/
void Disptree(Tree T);/*凹入表示法输出二叉树* /
void PreOrderTraverse(Tree T);/*前序遍历二叉树*/
void InOrderTraverse(Tree T);/*中序遍历二叉树*/
void PostOrderTraverse(Tree T);/*后序遍历二叉树*/
void TreeEmpty(Tree T);/*检查二叉树是否为空*/
void ClearTree(Tree T);/*清空一颗二叉树*/
int TreeDepth(Tree T);/*返回树的深度*/
TElementType Root(Tree T);/*返回根节点*/

/*前序遍历法创建一颗二叉树*/
Tree CreateBiTree(){
char ch = str[index++];
Tree T;
if (ch == '#')
T = NULL;
else{
T = malloc(sizeof(struct TreeNode));
T->data = ch;
T->LChild = CreateBiTree();
T->RChild = CreateBiTree();
}
return T;
}

/*前序遍历二叉树*/
void PreOrderTraverse(Tree T){
if (T != NULL){
printf("%c ", T->data);
PreOrderTraverse(T->LChild);
PreOrderTraverse(T->RChild);
}
}

/*中序遍历二叉树*/
void InOrderTraverse(Tree T){
if (T != NULL){
InOrderTraverse(T->LChild);
printf("%c ", T->data);
InOrderTraverse(T->RChild);
}
}

/*后序遍历二叉树*/
void PostOrderTraverse(Tree T){
if (T != NULL){
PostOrderTraverse(T->LChild);
PostOrderTraverse(T->RChild);
printf("%c ", T->data);
}
}

/*检查二叉树是否为空*/
void TreeEmpty(Tree T){
if (T == NULL)
printf("二叉树为空");
else
printf("二叉树不为空");
}

//凹入表示法输出二叉树
void Disptree(Tree T)
{
if (T)
{
printf("%c", T->data);
if (T->LChild || T->RChild)
{
printf("(");
Disptree(T->LChild);
if (T->RChild)
printf(",");
Disptree(T->RChild);
printf(")");
}
}
}

/*清空一颗二叉树*/
void ClearTree(Tree T){
if (T != NULL){
ClearTree(T->LChild);
ClearTree(T->RChild);
free(T);
}
return NULL;
}

/*返回树的深度*/
int TreeDepth(Tree T){
int left, right;
if (T == NULL)
return NULL;

if (T->LChild != NULL)
left = TreeDepth(T->LChild);
else
left = 0;

if (T->RChild != NULL)
right = TreeDepth(T->RChild);
else
right = 0;

return left > right ? left + 1 : right + 1;
}

/*返回根节点*/
TElementType Root(Tree T){
if (T != NULL)
return T->data;
}

void main(){
Tree T;
T = CreateBiTree();

printf("凹入表示法：\n");
Disptree(T);

printf("\n前序遍历：\n");
PreOrderTraverse(T);
printf("\n中序遍历：\n");
InOrderTraverse(T);
printf("\n后序遍历：\n");
PostOrderTraverse(T);

printf("\n树是否为空：");
TreeEmpty(T);
printf("\n树的深度为：%d", TreeDepth(T));
printf("\n树的根节点为：%c", Root(T));
}