Convert Sorted Array to Binary Search Tree

题目：

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

我的解法：

（1）算法思想：

二分法，数组的中间点为根节点，然后递归。

（2）代码如下：

/**
* 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 *convert(vector &num,int low,int high){
int mid= (low+high)/2;
TreeNode *node=new TreeNode(num[mid]);
if(low==high) return node;

if(lowleft=convert(num,low,mid-1);
if(midright=convert(num,mid+1,high);
return node;
}

TreeNode *sortedArrayToBST(vector &num) {
int len=num.size();
if(len==0) return NULL;
TreeNode *node=convert(num,0,len-1);
}
};