Convert Sorted Array to Binary Search Tree @LeetCode

PROBLEM :

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

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SIMPLE c++ IMPLEMENTATION :( Recursive Solution )
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/**
 * 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 {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        if(nums.size()==0)
            return NULL ;
        if(nums.size()==1){
            TreeNode *node=new TreeNode(nums[0]) ;
            return node ;
        }
     
        int mid=nums.size()/2 ;
        TreeNode* node=new TreeNode(nums[mid]) ;
     
        vector<int> LeftHalf(nums.begin(), nums.begin()+mid);
        vector<int> RightHalf(nums.begin()+mid+1, nums.end());
     
        node->left=sortedArrayToBST(LeftHalf) ;
        node->right=sortedArrayToBST(RightHalf) ;
     
        return node ;
    }
};

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SIMPLE c++ IMPLEMENTATION :(Iterative Solution - using divide-and-conquer )
--------------------------------------------------------------------------------

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

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