Here is source code of the C Program to Construct a Balanced Binary Tree using Sorted Array. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Construct a Balenced Binary Tree using Sorted Array
* 40
* / \
* 20 60
* / \ \
* 10 30 80
* \
* 90
* (Given Binary Search Tree)
*/
#include <stdio.h>
#include <stdlib.h>

struct btnode
{
int value;
struct btnode *l;
struct btnode *r;
};

typedef struct btnode N;
N* bst(int arr[], int first, int last);
N* new(int val);
void display(N *temp);

int main()
{
int arr[] = {10, 20, 30, 40, 60, 80, 90};
N *root = (N*)malloc(sizeof(N));
int n = sizeof(arr) / sizeof(arr[0]), i;

printf("Given sorted array is\n");
for (i = 0;i < n;i++)
printf("%d\t", arr[i]);
root = bst(arr, 0, n - 1);
printf("\n The preorder traversal of binary search tree is as follows\n");
display(root);
printf("\n");
return 0;
}

/* To create a new node */
N* new(int val)
{
N* node = (N*)malloc(sizeof(N));

node->value = val;
node->l = NULL;
node->r = NULL;
return node;
}

/* To create a balanced binary search tree */
N* bst(int arr[], int first, int last)
{
int mid;
N* temp = (N*)malloc(sizeof(N));
if (first > last)
return NULL;
mid = (first + last) / 2;
temp = new(arr[mid]);
temp->l = bst(arr, first, mid - 1);
temp->r = bst(arr, mid + 1, last);
return temp;
}

/* To display the preorder */
void display(N *temp)
{
printf("%d->", temp->value);
if (temp->l != NULL)
display(temp->l);
if (temp->r != NULL)
display(temp->r);
}


$ cc tree21.c
$ a.out
Given sorted array is
10 20 30 40 60 80 90
The preorder traversal of binary search tree is as follows
40->20->10->30->80->60->90