Convert Sorted Array to Binary Search Tree

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

方法： 类似于divide & conquer进行分析。

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {private:    void Create(vector<int>& nums,int left, int right, TreeNode*& root){        int middle = left + (right - left) / 2;        root = new TreeNode(nums[middle]);        if(left==right){            root->left = root -> right = NULL;            return;        }        else if(middle == left){            Create(nums, middle+1, right, root->right);        }        else{            Create(nums, left, middle - 1, root->left);            Create(nums, middle+1, right, root->right);        }    }public:    TreeNode* sortedArrayToBST(vector<int>& nums) {        if(nums.size()<1)            return NULL;        TreeNode* root;        Create(nums,0, nums.size()-1,root);        return root;    }};