链表的结构定义及基本操作

#include"stdlib.h"
#include"stdio.h"
struct treenode
{
treenode *left;
int data;
treenode *right;
};
//typedef struct tree treenode;
typedef treenode *b_tree;

b_tree insert_node(b_tree root , int node)
{
b_tree newnode;
b_tree currentnode;
b_tree parentnode;

newnode=(b_tree)malloc(sizeof(treenode));

newnode->data = node;
newnode->right=NULL;
newnode->left=NULL;
if(root == NULL)
return newnode;
else 
{
currentnode=root;
while(currentnode != NULL)
{
parentnode=currentnode;