怎样编写一个程序，把一个有序整数数组放到二叉树中？ 递归算法

#include "stdio.h"
#include "stdlib.h"
#include "string.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;
 
}