public TreeNode constructMaximumBinaryTree(int[] a) {
        if(a==null || a.length==0)return null;
        return go(a, 0, a.length-1);
    }
Definition for a binary tree node.
public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}
src/problems/medium/MaximumBinaryTree.java