怎样编写一个程序，把一个有序整数数组放到二叉树中

#include <stdio.h>

#include <stdlib.h>

struct student {

int value;

struct student *lchild;

struct student *rchild;

};

void arraytotree(int *a, int len, struct student **p) {

if(len) {

*p = (struct student*)malloc(sizeof(struct student));

(*p)->value = a[len/2];

arraytotree(a, len/2, &((*p)->lchild));

arraytotree(a+len/2+1, len-len/2-1, &((*p)->rchild));

} else {

*p = NULL;

}

}

void display_tree(struct student *head) {

if(head->lchild)display_tree(head->lchild);

printf("%d\t", head->value);

if(head->rchild)display_tree(head->rchild);

}

int main() {

int a[] = {1,2,3,4,9,10,33,56,78,90};

struct student *tree;

arraytotree(a, sizeof(a)/sizeof(a[0]), &tree);

printf("After convert:\n");

display_tree(tree);

printf("\n");

return 0;

}