数据结构第七章查找-树表的查找(二叉排序树的查找)

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

typedef struct
{
	char key;
}ElemType;
typedef struct BSTNode
{
	ElemType data;
	struct BSTNode* rchild,* lchild;
}BSTNode,*BSTree;
//插入元素
BSTree InsertBST(BSTree T, char key)
{
	if (T == NULL)
	{
		T = (BSTree)malloc(sizeof(BSTNode));
		T->data.key = key;
		T->lchild = T->rchild = NULL;
	}
	else if (key < T->data.key)
	{
		T->lchild = InsertBST(T->lchild, key);
	}
	else {
		T->rchild = InsertBST(T->rchild, key);
	}
	return T;
}
//查找函数
BSTree SearchBST(BSTree T, char key)
{
	if (T == NULL || T->data.key == key)
	{
		return T;
	}
	else if (key < T->data.key)
	{
		return SearchBST(T->lchild, key);
	}
	else
	{
		return SearchBST(T->rchild, key);
	}
}
//打印
void printBST(BSTree T)
{
	if (T)
	{
		printBST(T->lchild);
		printf("%c ", T->data.key);
		printBST(T->rchild);
	}
}
//释放空间
void FreeBST(BSTree T)
{
	if (T)
	{
		free(T->lchild);
		free(T->rchild);
		free(T);
	}
}
int main()
{
	BSTree root = NULL;
	char keys[] = {'D','B','A','C','E','F'};
	int n = sizeof(keys) / sizeof(keys[0]);
	for (int i = 0; i < n; i++)
	{
		root = InsertBST(root, keys[i]);
	}
	printf("打印如下\n");
	printBST(root);
	printf("\n");
	char keyNum = 'C';
	BSTree result = SearchBST(root, keyNum);
	if (result)
	{
		printf("找到了 %c 在BST中\n", result->data.key);
	}
	else
	{
		printf("找不到 %c 在BST中\n",keyNum);
	}
	FreeBST(root);
	return 0;
}

 

书本也提出了查找函数使用非递归方法，但是书本只给出了查找算法函数的代码，下面是使用非递归算法实现二叉排序查找

---

BSTree SearchBST(BSTree T, char key)
{
	while (T != NULL)
	{
		if (key == T->data.key)
		{
			return T;
		}
		else if (key < T->data.key)
		{
			T = T->lchild;
		}
		else
		{
			T = T->rchild;
		}
	}
	return NULL;
}