链式二叉树的创建销毁及其应用

因为层序遍历和判断是否为完全二叉树需要队列实现，所以要引入队列

Queue.h

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>

typedef int QDataType;

typedef struct QueueNode
{
	struct QueueNode* next;
	QDataType data;
}QueueNode;

typedef struct Queue
{
	QueueNode* head;
	QueueNode* tail;
	// size_t _size;
}Queue;

//void QueueInit(QueueNode** pphead, QueueNode** pptail);
void QueueInit(Queue* pq);
void QueueDestroy(Queue* pq);
void QueuePush(Queue* pq, QDataType x);
void QueuePop(Queue* pq);
QDataType QueueFront(Queue* pq);
QDataType QueueBack(Queue* pq);
int QueueSize(Queue* pq);
bool QueueEmpty(Queue* pq);

Queue.c

#define _CRT_SECURE_NO_WARNINGS 1
#include "Queue.h"

void QueueInit(Queue* pq)
{
	assert(pq);
	pq->head = NULL;
	pq->tail = NULL;
}
void QueueDestroy(Queue* pq)
{
	assert(pq);
	QueueNode* cur = pq->head;
	while (cur != NULL)
	{
		QueueNode* next = cur->next;
		free(cur);
		cur = next;
	}
	pq->head = pq->tail = NULL;
}
void QueuePush(Queue* pq, QDataType x)
{
	assert(pq);
	QueueNode* newnode = (QueueNode*)malloc(sizeof(QueueNode));
	newnode->data = x;
	newnode->next = NULL;
	if (pq->head == NULL)
	{
		pq->head = newnode;
		pq->tail = newnode;
	}
	else
	{
		pq->tail->next = newnode;
		pq->tail = newnode;
	}
}
void QueuePop(Queue* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	if (pq->head == pq->tail)
	{
		free(pq->head);
		pq->head = pq->tail = NULL;
	}
	else
	{
		QueueNode* next = pq->head->next;
		free(pq->head);
		pq->head = next;
	}
}
QDataType QueueFront(Queue* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	return pq->head->data;
}
QDataType QueueBack(Queue* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	return pq->tail->data;
}
int QueueSize(Queue* pq)
{
	assert(pq);
	int n = 0;
	QueueNode* cur = pq->head;
	while (cur)
	{
		cur = cur->next;
		n++;
	}
	return n;
}
bool QueueEmpty(Queue* pq)
{
	assert(pq);
	return pq->head == NULL;
}

接下来就是二叉树的实现

BinaryTree.h

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include "Queue.h"
typedef char BTDataType;

typedef struct BinaryTreeNode
{
	BTDataType data;
	struct BinaryTreeNode* left;
	struct BinaryTreeNode* right;
}BTNode;

// 通过前序遍历的数组"ABD##E#H##CF##G##"构建二叉树
BTNode* BinaryTreeCreate(BTDataType* a, int n, int* pi);
// 二叉树销毁
void BinaryTreeDestory(BTNode** root);
// 二叉树节点个数
int BinaryTreeSize(BTNode* root);
// 二叉树叶子节点个数
int BinaryTreeLeafSize(BTNode* root);
// 二叉树第k层节点个数
int BinaryTreeLevelKSize(BTNode* root, int k);
// 二叉树查找值为x的节点
BTNode* BinaryTreeFind(BTNode* root, BTDataType x);
// 二叉树前序遍历 
void BinaryTreePrevOrder(BTNode* root);
// 二叉树中序遍历
void BinaryTreeInOrder(BTNode* root);
// 二叉树后序遍历
void BinaryTreePostOrder(BTNode* root);
// 层序遍历
void BinaryTreeLevelOrder(BTNode* root);
// 判断二叉树是否是完全二叉树
int BinaryTreeComplete(BTNode* root);

BinaryTree.c

#define _CRT_SECURE_NO_WARNINGS 1
#include "BinaryTree.h"
#include "Queue.h"


// 通过前序遍历的数组"ABD##E#H##CF##G##"构建二叉树
BTNode* BinaryTreeCreate(BTDataType* a, int n, int* pi)
{
	if (a[*pi] == '#')
	{
		(*pi)++;
		return NULL;
	}
	BTNode* root = (BTNode*)malloc(sizeof(BTNode));
	root->data = a[*pi];
	(*pi)++;
	root->left = BinaryTreeCreate(a, n, pi);
	root->right = BinaryTreeCreate(a, n, pi);
	return root;
}
// 二叉树销毁
void BinaryTreeDestory(BTNode** root)
{
	if (*root) {
		BinaryTreeDestory(&((*root)->left));
		BinaryTreeDestory(&((*root)->right));
		free(*root);
	}
	*root = NULL;
}
// 二叉树节点个数
int BinaryTreeSize(BTNode* root)
{
	if (root == NULL)
	{
		return 0;
	}
	return BinaryTreeSize(root->left) + BinaryTreeSize(root->right) + 1;
}
// 二叉树叶子节点个数
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);
}
// 二叉树第k层节点个数
int BinaryTreeLevelKSize(BTNode* root, int k)
{
	if (root == NULL)
	{
		return NULL;
	}
	if (k == 1)
	{
		return 1;
	}
	return BinaryTreeLevelKSize(root->left, k - 1) + BinaryTreeLevelKSize(root->right, k - 1);
}
// 二叉树查找值为x的节点
BTNode* BinaryTreeFind(BTNode* root, BTDataType x)
{
	if (root == NULL)
	{
		return NULL;
	}
	if (root->data == x)
	{
		return root;
	}
	BTNode* leftRet = BinaryTreeFind(root->left, x);
	if (leftRet)
	{
		return leftRet;
	}
	BTNode* rightRet = BinaryTreeFind(root->right, x);
	if (rightRet)
	{
		return rightRet;
	}
	return NULL;
}
// 二叉树前序遍历 
void BinaryTreePrevOrder(BTNode* root)
{
	if (root == NULL)
	{
		return NULL;
	}
	printf("%c ", root->data);
	BinaryTreePrevOrder(root->left);
	BinaryTreePrevOrder(root->right);
}
// 二叉树中序遍历
void BinaryTreeInOrder(BTNode* root)
{
	if (root == NULL)
	{
		return NULL;
	}
	BinaryTreePrevOrder(root->left);
	printf("%c ", root->data);
	BinaryTreePrevOrder(root->right);
}
// 二叉树后序遍历
void BinaryTreePostOrder(BTNode* root)
{
	if (root == NULL)
	{
		return NULL;
	}
	BinaryTreePrevOrder(root->left);
	BinaryTreePrevOrder(root->right);
	printf("%c ", root->data);
}
// 层序遍历
void BinaryTreeLevelOrder(BTNode* root)
{
	if (root == NULL)
	{
		return;
	}
	Queue q;
	QueueInit(&q);
	QueuePush(&q, root);
	while (!QueueEmpty(&q))
	{
		BTNode* front = QueueFront(&q);
		QueuePop(&q);
		printf("%c ", front->data);
		if (front->left)
		{
			QueuePush(&q, front->left);
		}
		if (front->right)
		{
			QueuePush(&q, front->right);
		}
		if (front == NULL && !QueueEmpty(&q))
		{
			return false;
		}
	}
	printf("\n");
	QueueDestroy(&q);
}
// 判断二叉树是否是完全二叉树
int BinaryTreeComplete(BTNode* root)
{
	if (root == NULL)
	{
		return;
	}
	Queue q;
	QueueInit(&q);
	QueuePush(&q, root);
	while (!QueueEmpty(&q))
	{
		BTNode* front = QueueFront(&q);
		QueuePop(&q);
		printf("%c ", front->data);
		if (front)
		{
			QueuePush(&q, front->left);
			QueuePush(&q, front->right);
		}
		else
		{
			break;
		}
	}
	while (!QueueEmpty(&q))
	{
		BTNode* front = QueueFront(&q);
		QueuePop(&q);
		printf("%c ", front->data);
		if (front)
		{
			QueueDestroy(&q);
			return false;
		}

	}

	QueueDestroy(&q);
	return true;
}

test.c

#define _CRT_SECURE_NO_WARNINGS 1
#include "BinaryTree.h"

int main()
{
	char str[] = "ABD##E#H##CF##G##";
	int len = strlen(str);
	int i = 0;
	BTNode* root = BinaryTreeCreate(str, len, &i);
	BinaryTreePrevOrder( root);
	BinaryTreeDestory(&root);
	return 0;
}