二叉树的遍历

#include"iostream"
#include"stdlib.h"
using namespace std;

struct  tree
{
    int data;
    struct tree *left;
    struct tree *right;
};

typedef  struct tree treenode;
typedef  treenode *btree;


/*------插入二叉树的结点-------*/
btree  insertnode(btree root,int value)
{
    btree newnode;
    btree current;
    btree back;


    /*---创建新结点内存---*/

    newnode=(btree)malloc(sizeof(treenode));
    newnode->data=value;
    newnode->right=NULL;
    newnode->left=NULL;

    if(root==NULL)
    {
        return newnode;
    }
    else 
    {
        current=root;
        while(current!=NULL)
        {
            back=current;
            if(current->data>value)
                current=current->left;
            else 
                current=current->right;
        }
        if(back->data>value)
            back->left=newnode;
        else
            back->right=newnode;
    }
    return root;
}

/*------创建二叉树--------*/

btree  createbtree(int *data, int len)
{
    btree root =NULL;
    int i;
    for(i=0;i<len;i++)
        root=insertnode(root,data[i]);
    return root;
}
/*-----中序遍历------*/
void  inorder( btree ptr)
{
    if(ptr!=NULL)
    {
        inorder(ptr->left);
        printf("[%2d]\n",ptr->data);
        inorder(ptr->right);
    }
}
/*-----------------------*/

/*--------前序遍历-------*/

void  preorder(btree ptr)
{
    if(ptr!=NULL)
    {
       
        printf("[%2d]\n",ptr->data);
        inorder(ptr->left);
        inorder(ptr->right);
    }
}
/*-----------------------------*/

/*------后序遍历--------*/

void  postorder(btree ptr)
{
    if(ptr!=NULL)
    {
       
        inorder(ptr->left);
        inorder(ptr->right);
        printf("[%2d]\n",ptr->data);
        
    }
}
/*---------------------------*/

/*---------主程序-----*/

int  main()
{
    btree root=NULL;

    int data[9]={5,6,4,8,2,3,7,1,9};
    root =createbtree(data,9);
    printf("树的结点内容：\n");
    inorder(root);
    cout<<endl;
    preorder(root);
    cout<<endl;
    postorder(root);
    cout<<endl;

}