Program to build a binary search tree from an array

/* Program to build a binary search tree from an array. */

#include <stdio.h>
#include <conio.h>
#include <alloc.h>

struct node
{
struct node *left ;
char data ;
struct node *right ;
} ;

struct node * buildtree ( int ) ;
void inorder ( struct node * ) ;

char a[ ] = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', '\0', '\0', 'H', '\0',
'\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0'
} ;

void main( )
{
struct node *root ;

clrscr( ) ;

root = buildtree ( 0 ) ;
printf ( "In-order Traversal:\n" ) ;
inorder ( root ) ;

getch( ) ;
}
struct node * buildtree ( int n )
{
struct node *temp = NULL ;
if ( a[n] != '\0' )
{
temp = ( struct node * ) malloc ( sizeof ( struct node ) ) ;
temp -> left = buildtree ( 2 * n + 1 ) ;
temp -> data = a[n] ;
temp -> right = buildtree ( 2 * n + 2 ) ;
}
return temp ;
}

void inorder ( struct node *root )
{
if ( root != NULL )
{
inorder ( root -> left ) ;
printf ( "%c\t", root -> data ) ;
inorder ( root -> right ) ;
}
}