[leetcode]Convert Sorted Array to Binary Search Tree

public class Solution {
public TreeNode sortedArrayToBST(int[] num) {
return partialConvert(num, 0, num.length-1);
}

private TreeNode partialConvert(int[] num, int left, int right)
{
if (left > right) return null;
if (left == right)
{
return new TreeNode(num[left]);
}
// else
{
int mid = (left + right) / 2;
TreeNode node = new TreeNode(num[mid]);
node.left = partialConvert(num, left, mid-1);
node.right= partialConvert(num, mid+1, right);
return node;
}
}
}