二叉排序树

二叉排序树又叫二叉查找树。

遵循三个原则：

1、一棵树要么为空，要么

2、左孩子节点小于根节点值，根节点值小于右孩子节点值

3、子树也具备这个规则

代码：

#include <iostream>

#include <cstdlib>



using namespace std;

static int flag=0;

typedef struct binst

{

	int data;

	struct binst *lchild;

	struct binst *rchild;

}*BST;



void createBST(BST &bst,int key)

{

	BST t,p,pre;

	t=(BST)malloc(sizeof(struct binst));

	if(!t)

	{

	   cout<<"allocate fail";

	   return;

	}

	t->data=key;

	t->lchild=NULL;

	t->rchild=NULL;

	if(bst==NULL)

	{

		bst=t;

	}

	else

	{

	p=bst;

	while(p)

	{

		if(p->data==key)

		{

			free(t);

			return;

		}

		else if(p->data<key)

		{

			pre=p;

			p=p->rchild;

		}

		else

		{

			pre=p;

			p=p->lchild;

		}

	}

	if(pre->data<key)

	{

		pre->rchild=t;

	}

	else

	{

		pre->lchild=t;

	}

	}

}



void bstSearch(BST bst,int key)

{

	

	if(bst)

	{

		if(bst->data==key)

		{

			flag=1;

			cout<<"search success!"<<endl;

			return;

		}

		else if(bst->data<key)

		{

			bstSearch(bst->rchild,key);

		}

		else

		{

			bstSearch(bst->lchild,key);

		}

	}

	if(flag==0)

	{

		cout<<"search fail!"<<endl;

	}

}

void preOrderSearch(BST bst)

{

	if(bst)

	{

		cout<<bst->data<<"  ";

		preOrderSearch(bst->lchild);

		preOrderSearch(bst->rchild);

	}

}



int main()

{

	BST bst=NULL;

	int arr[]={12,3,5,17,15,19,20};

	int key;

	cout<<"create the BST"<<endl;

	for(int i=0;i<7;i++)

	{

		createBST(bst,arr[i]);

	}

	cout<<"output the bst:"<<endl;

	preOrderSearch(bst);

	cout<<endl;

	cout<<"please input the key:";

	cin>>key;

	bstSearch(bst,key);

	cout<<endl;

	return 0;



}

 运行截图：