[Leetcode] Convert Sorted Array to Binary Search Tree

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedArrayToBST(int[] num) {
        int N=num.length;
        if(N<1)
            return null;
        return myTree(num, 0, N-1);
    }

    private TreeNode myTree(int[] num, int low, int high) {
        // TODO Auto-generated method stub
        if(low>high)
            return null;
        int mid=(low+high)/2;
        TreeNode root=new TreeNode(num[mid]);
        root.left=myTree(num,low,mid-1);
        root.right=myTree(num, mid+1, high);
        return root;
    }
}