查找算法--二叉排序树算法（C++实现完整代码）

如下图所示是某个排序二叉树，什么是排序二叉树？。。。
下面的算法实现的是查找某个关键字是否在这棵树上的某个节点中。算法分为俩个部分，第一部分为二叉排序树的创建，第二部分是二叉排序树查找算法；

#include <iostream>
using namespace std;
typedef struct BTNode
{
	int key;
	struct BTNode *lchild;
	struct BTNode *rchild;
}BTNode;

//注意！这不是二叉排序树构造算法，这个二叉排序树生成只是为了下面的二叉排序树查找算法服务，真正的二叉排序树构造算法自行查找。
void createBST(BTNode *&bt)
{
	//欲生成的二叉排序树如上图所示
	bt = (BTNode*)malloc(sizeof(BTNode));
	bt->key = 5;
	
	BTNode* n4 = (BTNode*)malloc(sizeof(BTNode));
	n4->key = 4;
	BTNode* n8 = (BTNode*)malloc(sizeof(BTNode));
	n8->key = 8;
	BTNode* n3 = (BTNode*)malloc(sizeof(BTNode));
	n3->key = 3;
	BTNode* n7 = (BTNode*)malloc(sizeof(BTNode));
	n7->key = 7;
	BTNode* n9 = (BTNode*)malloc(sizeof(BTNode));
	n9->key = 9;
	BTNode* n10 = (BTNode*)malloc(sizeof(BTNode));
	n10->key = 10;
	
	bt->lchild = n4;
	bt->rchild = n8;
	n4->lchild = n3;
	n4->rchild = NULL;
	n8->lchild = n7;
	n8->rchild = n9;
	n3->lchild = NULL;
	n3->rchild = NULL;
	n7->lchild = NULL;
	n7->rchild = NULL;
	n9->lchild = NULL;
	n9->rchild = n10;
	n10->lchild = NULL;
	n10->rchild = NULL;
	//二叉排序树建立完成
}
BTNode* BSTSearch(BTNode* bt, int key)
{
	if (bt == NULL)
		return NULL;
	if (bt->key == key)
		return bt;			//返回关键字所在的结点指针
	else if(bt->key > key)
		return BSTSearch(bt->lchild, key);  //去左子树中查找
	else
		return BSTSearch(bt->rchild, key);
}
int main()
{
	BTNode *bt;
	createBST(bt);
	BTNode *p = BSTSearch(bt, 6);
	if (p == NULL)
		cout << "没有找到" << endl;
	else
		cout << "找到了 " << p->key << endl;
	return 0;
}