Convert Sorted Array to Balanced Binary Search Tree (BST)

(http://leetcode.com/2010/11/convert-sorted-array-into-balanced.html)

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

Code:

BinaryTree* sortedArrayToBST(int arr[], int start, int end)
{
    if (start > end)
        return NULL;
    int mid = start + (end - start) / ;
    BinaryTree* node = new BinaryTree(arr[mid]);
    node->left = sortedArrayToBST(arr, start, mid-);
    node->right = sortedArrayToBST(arr, mid+, end);
    return node;
}

BinaryTree* sortedArrayToBST(int arr[], int n)
{
    return sortedArrayToBST(arr, , n-);
}