Convert Sorted Array to Binary Search Tree

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

cpp:

class Solution {
public:
TreeNode* sortedArrayToBST(vector<int>& nums) {
if (nums.empty())
return nullptr;
int l = 0;
int r = nums.size() - 1;
if (l == r)
return new TreeNode(nums[l]);
int m = (r >> 1);
TreeNode *root = new TreeNode(nums[m]);

helper(l, m - 1, root, nums, 0);
helper(m + 1, r, root, nums, 1);
return root;
}

void helper(int l, int r, TreeNode* root, vector<int>& nums,
int LeftorRight) {
if (l > r)
return;
if (l == r) {
if (LeftorRight == 0) {
root->left = new TreeNode(nums[l]);
} else {
root->right = new TreeNode(nums[l]);
}
return;
}
TreeNode *curNode;
int m = l + ((r - l) >> 1);
if (LeftorRight == 0) {
root->left = new TreeNode(nums[m]);
curNode = root->left;
} else {
root->right = new TreeNode(nums[m]);
curNode = root->right;
}
helper(l, m - 1, curNode, nums, 0);
helper(m + 1, r, curNode, nums, 1);
}
};

java:

public class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
int len = nums.length;
if (len == 0)
return null;

int l = 0;
int r = len - 1;
int m = l + ((r - l) >> 1);

if (l == r)
return new TreeNode(nums[l]);

TreeNode root = new TreeNode(nums[m]);

helper(l, m - 1, root, nums, 0);
helper(m + 1, r, root, nums, 1);

return root;

}

public void helper(int l, int r, TreeNode root, int[] nums, int LeftorRight) {
if (l > r)
return;
if (l == r) {
if (LeftorRight == 0)
root.left = new TreeNode(nums[l]);
else
root.right = new TreeNode(nums[l]);
return;
}
int m = l + ((r - l) >> 1);
TreeNode curNode = new TreeNode(nums[m]);
if (LeftorRight == 0)
root.left = curNode;
else
root.right = curNode;

helper(l, m - 1, curNode, nums, 0);
helper(m + 1, r, curNode, nums, 1);

}
}