> 使用recursive方法进行二分，利用BST的特性

myCode.cpp

//Runtime: 24 ms, faster than 89.44%
//Memory Usage: 21.1 MB, less than 56.68%

class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return sortedArrayToBST(nums,0,nums.size());
    }
    TreeNode* sortedArrayToBST(vector<int>& nums,int start,int end){
        if(end <= start) return NULL;
        int midIdx = (end + start) / 2;
        TreeNode* root = new TreeNode(nums[midIdx]);
        root->left = sortedArrayToBST(nums,start,midIdx);
        root->right = sortedArrayToBST(nums,midIdx + 1,end);
        return root;
    }
};