编写递归算法,在二叉树中求位于先序序列中第k个位置的结点的值

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
static int n=0;
typedef struct tree
{
struct tree *left;
int date;
struct tree *right;
}treenode,*b_tree;
///////插入节点/////////////////////

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

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

newnode->date=node;
newnode->right=NULL;
newnode->left=NULL;

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