108. Convert Sorted Array to Binary Search Tree

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