二叉树基本接口的实现

首先声明结构体

#pragma once
#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
#include<assert.h>
typedef char BTDataType;
typedef struct BinaryTreeNode
{
	BTDataType _data;
	struct BinaryTreeNode* _left;
	struct BinaryTreeNode* _right;
}BTNode;

然后声明一些基本的接口

BTNode* BinaryTreeCreate(BTDataType* a,int *pindex);//创建二叉树
void BinaryTreeDestory(BTNode* root);//销毁二叉树
int BinaryTreeSize(BTNode* root);//计算二叉树的结点个数
int BinaryTreeLeafSize(BTNode* root);//计算二叉树叶子结点的个数
int BinaryTreeLevelkSize(BTNode* root, int k);//计算第k层结点的个数
BTNode* BinaryTreeFind(BTNode* root, BTDataType x);//找到元素为x的结点，并返回该指针
void BinaryTreePreorder(BTNode* root);//先序遍历
void BinaryTreeInorder(BTNode* root);//中序遍历
void BinaryTreePostorder(BTNode* root);//后序遍历

#include"BinaryTree.h"
BTNode* BinaryTreeCreate(BTDataType* a, int *pindex)
{
	assert(a);
	if (a[*pindex] == '#')
	{
		++(*pindex);
		return NULL;
	}
	else
	{
		BTNode* root = (BTNode*)malloc(sizeof(BTNode));
		root->_data = a[*pindex];
		++(*pindex);
		root->_left = BinaryTreeCreate(a, pindex);
		root->_right = BinaryTreeCreate(a, pindex);
		return root;
	}
}

void BinaryTreeDestory(BTNode* root)
{
	if (root == NULL)
		return;
	BinaryTreeDestory(root->_left);
	BinaryTreeDestory(root->_right);
	free(root);
	root = NULL;
}

int BinaryTreeSize(BTNode* root)
{
	if (root == NULL)
		return 0;
	else
	{
		return 1 + BinaryTreeSize(root->_left) + BinaryTreeSize(root->_right);
	}
}

int BinaryTreeLeafSize(BTNode* root)
{
	
	if (root == NULL)
	{
		return 0;
	}
	if (root->_left == NULL && root->_right == NULL)
		return 1;
	return BinaryTreeLeafSize(root->_left) + BinaryTreeLeafSize(root->_right);
}
int BinaryTreeLevelkSize(BTNode* root, int k)
{
	if (root == NULL)
	{
		return 0;
	}
	if (k == 1)
	{
		return 1;
	}
	return BinaryTreeLevelkSize(root->_left, k - 1) + BinaryTreeLevelkSize(root->_right, k - 1);
}
BTNode* BinaryTreeFind(BTNode* root, BTDataType x)
{
	if (root == NULL)
		return NULL;
	if (root->_data == x)
		return root;
	BTNode* ret;
	ret=BinaryTreeFind(root->_left, x);
	if (ret)
		return ret;
	ret = BinaryTreeFind(root->_right, x);
	if (ret)
	return ret;
  return NULL;
}

void BinaryTreePreorder(BTNode* root)
{
	if (root == NULL)
		return;
	printf("%c ", root->_data);
	BinaryTreePreorder(root->_left);
	BinaryTreePreorder(root->_right);
}
void BinaryTreeInorder(BTNode* root)
{
	if (root == NULL)
		return;
	BinaryTreeInorder(root->_left);
	printf("%c ", root->_data);
	BinaryTreeInorder(root->_right);
}

void BinaryTreePostorder(BTNode* root)
{
	if (root == NULL)
		return;
	BinaryTreePostorder(root->_left);
	BinaryTreePostorder(root->_right);
	printf("%c ", root->_data);
}

main函数中测试结果

#include"BinaryTree.h"
int main()
{
	char a[] = "ABD##E#H##CF##G##";
	int index = 0;
	BTNode* tree = BinaryTreeCreate(a,&index);
	BinaryTreePreorder(tree);
	printf("\n");
	BinaryTreeInorder(tree);
	printf("\n");
	BinaryTreePostorder(tree);
	printf("\n");
	printf("%d\n", BinaryTreeSize(tree));
	printf("%d\n", BinaryTreeLeafSize(tree));
	printf("%d\n", BinaryTreeLevelkSize(tree,4));
	BinaryTreeDestory(tree);
	tree = NULL;
	return 0;
}

运行结果如下所示：