文章目录

• 一、前言
• 二、二叉树的遍历
• • 前中后序
• 三、求二叉树结点个数
• 四、求二叉树深度
• 五、第k层节点个数
• 六、返回某个节点的地址
• 七、总结

一、前言

• 因为普通的二叉树增删查改没有任何意义，总不能只是因为结构复杂就用这个没有任何意义的普通二叉树来存储数据，所以我们不进行它的增删查改学习，而是先了解了解普通二叉树的一些操作：求二叉树节点个数、深度等等。

二、二叉树的遍历

前中后序

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

typedef struct BTNode
{
	struct BTNode* left;
	struct BTNode* right;
	int data;
}BTNode;

BTNode* BuyNewnode(int x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc error");
		assert(newnode);
	}
	newnode->data = x;
	newnode->left = NULL;
	newnode->right = NULL;
	return newnode;
}

BTNode* BTCreat()
{
	BTNode* node1 = BuyNewnode(1);
	BTNode* node2 = BuyNewnode(2);
	BTNode* node3 = BuyNewnode(4);
	BTNode* node4 = BuyNewnode(3);
	BTNode* node5 = BuyNewnode(5);
	BTNode* node6 = BuyNewnode(6);

	node1->left = node2;
	node1->right = node3;
	node2->left = node4;
	node3->left = node5;
	node4->right = node6;
	
	return node1;
}

//前序
void PreOrder(BTNode* n1)
{
	if (n1 == NULL)
	{
		printf("NULL ");
		return;
	}
	printf("%d ", n1->data);
	PreOrder(n1->left);
	PreOrder(n1->right);
}

//中序
void InOrder(BTNode* n1)
{
	if (n1 == NULL)
	{
		printf("NULL ");
		return;
	}
	InOrder(n1->left);
	printf("%d ", n1->data);
	InOrder(n1->right);
}

//后序
void PostOrder(BTNode* n1)
{
	if (n1 == NULL)
	{
		printf("NULL ");
		return;
	}
	PostOrder(n1->left);
	PostOrder(n1->right);
	printf("%d ", n1->data);
}

int main()
{
	BTNode* n1 = BTCreat();

	//前序
	PreOrder(n1);
	printf("\n");
	
	//中序
	InOrder(n1);
	printf("\n");

	//后序
	PostOrder(n1);
	printf("\n");
	
	return 0;
}

三、求二叉树结点个数

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

typedef struct BTNode
{
	struct BTNode* left;
	struct BTNode* right;
	int data;
}BTNode;

BTNode* BuyNewnode(int x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc error");
		assert(newnode);
	}
	newnode->data = x;
	newnode->left = NULL;
	newnode->right = NULL;
	return newnode;
}

BTNode* BTCreat()
{
	BTNode* node1 = BuyNewnode(1);
	BTNode* node2 = BuyNewnode(2);
	BTNode* node3 = BuyNewnode(4);
	BTNode* node4 = BuyNewnode(3);
	BTNode* node5 = BuyNewnode(5);
	BTNode* node6 = BuyNewnode(6);

	node1->left = node2;
	node1->right = node3;
	node2->left = node4;
	node3->left = node5;
	node4->right = node6;
	
	return node1;
}

int BTSize(BTNode* n1)
{
	if (n1 == NULL)
		return 0;
	return BTSize(n1->left) + BTSize(n1->right) + 1;
}

int main()
{
	BTNode* n1 = BTCreat();
	//二叉树节点个数
	int size = BTSize(n1);
	printf("%d\n", size);
	return 0;
}

四、求二叉树深度

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

typedef struct BTNode
{
	struct BTNode* left;
	struct BTNode* right;
	int data;
}BTNode;

BTNode* BuyNewnode(int x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc error");
		assert(newnode);
	}
	newnode->data = x;
	newnode->left = NULL;
	newnode->right = NULL;
	return newnode;
}

BTNode* BTCreat()
{
	BTNode* node1 = BuyNewnode(1);
	BTNode* node2 = BuyNewnode(2);
	BTNode* node3 = BuyNewnode(4);
	BTNode* node4 = BuyNewnode(3);
	BTNode* node5 = BuyNewnode(5);
	BTNode* node6 = BuyNewnode(6);

	node1->left = node2;
	node1->right = node3;
	node2->left = node4;
	node3->left = node5;
	node4->right = node6;
	
	return node1;
}
int BinaryTreeHeight(BTNode* n1)
{
	if (n1 == NULL)
		return 0;

	int BTLeft = BinaryTreeHeight(n1->left);
	int BTRight = BinaryTreeHeight(n1->right);

	return BTLeft > BTRight ? BTLeft + 1: BTRight + 1;
}
int main()
{
	BTNode* n1 = BTCreat();
	//二叉树深度
	int BTHeight = BinaryTreeHeight(n1);
	printf("%d\n", BTHeight);
	return 0;
}

五、第k层节点个数

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

typedef struct BTNode
{
	struct BTNode* left;
	struct BTNode* right;
	int data;
}BTNode;

BTNode* BuyNewnode(int x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc error");
		assert(newnode);
	}
	newnode->data = x;
	newnode->left = NULL;
	newnode->right = NULL;
	return newnode;
}

BTNode* BTCreat()
{
	BTNode* node1 = BuyNewnode(1);
	BTNode* node2 = BuyNewnode(2);
	BTNode* node3 = BuyNewnode(4);
	BTNode* node4 = BuyNewnode(3);
	BTNode* node5 = BuyNewnode(5);
	BTNode* node6 = BuyNewnode(6);

	node1->left = node2;
	node1->right = node3;
	node2->left = node4;
	node3->left = node5;
	node4->right = node6;
	
	return node1;
}
int BTKLevel(BTNode* n1,int k)
{
	if (n1 == NULL)
		return 0;
	if (k == 1)
		return 1;

	return BTKLevel(n1->left,k-1) + BTKLevel(n1->right,k-1);
}
int main()
{
	BTNode* n1 = BTCreat();
	//第K层有几个节点
	int k = BTKLevel(n1,4);
	printf("%d\n", k);
	return 0;
}

六、返回某个节点的地址

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

typedef struct BTNode
{
	struct BTNode* left;
	struct BTNode* right;
	int data;
}BTNode;

BTNode* BuyNewnode(int x)
{
	BTNode* newnode = (BTNode*)malloc(sizeof(BTNode));
	if (newnode == NULL)
	{
		perror("malloc error");
		assert(newnode);
	}
	newnode->data = x;
	newnode->left = NULL;
	newnode->right = NULL;
	return newnode;
}

BTNode* BTCreat()
{
	BTNode* node1 = BuyNewnode(1);
	BTNode* node2 = BuyNewnode(2);
	BTNode* node3 = BuyNewnode(4);
	BTNode* node4 = BuyNewnode(3);
	BTNode* node5 = BuyNewnode(5);
	BTNode* node6 = BuyNewnode(6);

	node1->left = node2;
	node1->right = node3;
	node2->left = node4;
	node3->left = node5;
	node4->right = node6;
	
	return node1;
}
BTNode* BTFind(BTNode* n1,int x)
{
	if (n1 == NULL)
		return NULL;

	if (n1->data == x)
		return n1;

	BTNode* left = BTFind(n1->left,x);
	if (left)
		return left;
	BTNode* right = BTFind(n1->right,x);
	if (right)
		return right;
	return NULL;

}
int main()
{
	BTNode* n1 = BTCreat();
	//返回某个值的位置
	BTNode* p = BTFind(n1,9);
	if(p!=NULL)
		printf("%p\n", p);
	return 0;
}

七、总结

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