Given an array where elements are sorted in ascending order, convert it to a height balanced BST. http://leetcode.com/onlinejudge

leetcode_convert_sorted_array_to_binary_search_tree.cpp

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *get_bst_(vector<int>::iterator left, vector<int>::iterator right) {
        int n = right - left;
        if (0 == n) {
            return NULL;
        }
        TreeNode *node = new TreeNode( *(left + n/2) );
        node->left = get_bst_(left, left + n/2);
        node->right = get_bst_(left + n/2 + 1, right);
        return node;
    }

    TreeNode *sortedArrayToBST(vector<int> &num) {
        return get_bst_(num.begin(), num.end());
    }
};