数据结构之二叉排序树

二叉排序树的建立思想是比较简单的，即首先建立一个根结点，然后插入值比根节点值小，就成为根节点的左孩子，比它值大则成为根节点的右孩子。

需要注意的就是我们应该对它的左右孩子是否为空进行判断，如果为空，则要建立新的结点；如果不为空，则直接赋值过去即可。

#include<stdio.h>
#include<stdlib.h>
#define size 7
typedef struct BNode
{
		int key;
		struct BNode* rightchild;
		struct BNode* leftchild;
}*BNPtr;
int data[size] = { 45, 24, 53, 45, 12, 46, 90 };
BNPtr BST()
{
	int i;
	BNPtr root;
	BNPtr temPtr;
	BNPtr tempNewPtr;
	root = (BNPtr)malloc(sizeof(struct BNode));
	root->leftchild = NULL;
	root->rightchild = NULL;
	root->key = data[0];
	for (i = 1; i<size; i++)
	{
		temPtr = root;
		while (temPtr != NULL)
		{
			if (data[i] == temPtr->key)
			{
				printf("%d exist\n", data[i]);
				break;
			}
			else if (data[i]<temPtr->key)
			{
				if (temPtr->leftchild == NULL)
				{
					tempNewPtr = (BNPtr)malloc(sizeof(struct BNode));
					tempNewPtr->leftchild = NULL;
					tempNewPtr->rightchild = NULL;
					tempNewPtr->key = data[i];
					temPtr->leftchild = tempNewPtr;
					printf("%d  is the %d 's leftchild\r\n", data[i], temPtr->key);
					break;
				}
				else
				{
					temPtr = temPtr->leftchild;			
				}
				
	
			}
			else
			{
				if (temPtr->rightchild == NULL)
				{
					tempNewPtr = (BNPtr)malloc(sizeof(struct BNode));
					tempNewPtr->leftchild = NULL;
					tempNewPtr->rightchild = NULL;
					tempNewPtr->key = data[i];
					temPtr->rightchild = tempNewPtr;
					printf("%d  is the %d 's rightchild\r\n", data[i], temPtr->key);
					break;
				}
				else
				{
					temPtr = temPtr->rightchild;
				}
			}
		}
	}
	return root;
}
void inorder(BNPtr temPtr)
{
	if (temPtr->leftchild != NULL)
	{
		inorder(temPtr->leftchild);
	}
	printf("%d\n", temPtr->key);
	if (temPtr->rightchild != NULL)
	{
		inorder(temPtr->rightchild);
	}
}
	
int main()
{
	BNPtr temPtr;
	temPtr = BST();
	printf("中序遍历：\n");
	inorder(temPtr);
	return 0;
}