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struct TreeNode {	int val;	TreeNode *left;	TreeNode *right;	TreeNode(int x) : val(x), left(NULL), right(NULL) {}};class Solution {public:	TreeNode* Convert2BST(vector
   
    & num, int start, int end)	{		if(start > end)			return NULL;		int mid = (start+end)/2;		TreeNode* pNode = new TreeNode(num[mid]);		pNode->left = Convert2BST(num, start, mid-1);		pNode->right = Convert2BST(num, mid+1, end);		return pNode;	}    TreeNode *sortedArrayToBST(vector
    
      &num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        return Convert2BST(num, 0, num.size()-1);    }};
    
   

second time

/** * 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* sortedArrayToBSTUtil(vector
   
    & num, int start, int end)    {        if(start > end) return NULL;        int mid = start+(end-start)/2;        TreeNode* root = new TreeNode(num[mid]);        root->left = sortedArrayToBSTUtil(num, start, mid-1);        root->right = sortedArrayToBSTUtil(num, mid+1, end);        return root;    }    TreeNode *sortedArrayToBST(vector
    
      &num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        return sortedArrayToBSTUtil(num, 0, num.size()-1);    }};
    
   

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