#include <stdio.h>

 #include <stdlib.h>

 struct Tag_Node

 {

     struct Tag_Node *left;

     struct Tag_Node *right;

     int value;

 };

 typedef struct Tag_Node TNode;

 TNode* root = NULL;

 void append(int N);

 void print();

 int main()

 {

     append();

     append();

     append();

     append();

     append();

     append();

     append();

     printf("head:%d\n", root->value);

     print();

     getchar();

 }

 void append(int N)

 {

     TNode *NewNode = (TNode *)malloc(sizeof(TNode));

     NewNode->value = N;

     NewNode->left = NULL;//初始化这里很重要

     NewNode->right = NULL;

     if (root == NULL)

     {

         root = NewNode;//就指向根节点

         return;

     }

     else

     {

         TNode *temp =  NULL;

         temp = root;

         while ((N >= temp->value&&temp->left != NULL)||(N<temp->value&&temp->right!=NULL))

         {

             while (N >= temp->value&&temp->left != NULL)

             {

                 temp = temp->left;

             }

             while (N <= temp->value&&temp->right != NULL)

             {

                 temp = temp->right;

             }

         }

         if (N >= temp->value)

         {

             temp->left = NewNode;

             NewNode->right = temp;//形成双向链表

         }

         else

         {

             temp->right = NewNode;

             NewNode->left = temp;

         }

         return;

     }

 }

 void print()

 {

     TNode* leftside = NULL;

     if (root == NULL)

     {

         printf("there is not any element");

         return;

     }

     leftside = root->left;

     while ()

     {

         if (leftside->left == NULL)

         {

             break;

         }

         leftside = leftside->left;

     }

     while (leftside != NULL)

     {

         printf("%d ", leftside->value);

         leftside = leftside->right;

     }

 }