Convert Sorted Array to Binary Search Tree (LeetCode)---递归建立二叉搜索树

description：

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

code：Hint:类似于二分搜索，找到中点值作为根，再递归地建立左右子树

/** * 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 *sortedArrayToBST(vector<int> &num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(num.size() == 0)        {            return NULL;        }        return sorted2bst(num,0,num.size()-1);            }    TreeNode *sorted2bst(vector<int> &num, int st, int end)    {        if(st<=end)        {            int mid = (st+end)>>1;            TreeNode *root = new TreeNode(num[mid]);            root->left = sorted2bst(num,st,mid-1);            root->right = sorted2bst(num,mid+1,end);            return root;        }        else return NULL;    }};