private int maxDiff(Nodi root, int k)
{
min_diff = 9999999;
min_diff_key = -1;
maxDiffUtil(root, k);
return(min_diff);
}
public void Main()
{
Nodi root = new Nodi(9);
root.Left = new Nodi(4);
root.Right = new Nodi(17);
root.Left.Left = new Nodi(3);
root.Left.Right = new Nodi(6);
root.Left.Right.Left = new Nodi(5);
root.Left.Right.Right = new Nodi(7);
root.Right.Right = new Nodi(22);
root.Right.Right.Left = new Nodi(20);
Console.WriteLine($"k=4 result={maxDiff(root, 4)} expected=17");
Console.WriteLine($"k=18 result={maxDiff(root, 18)} expected=17");
Console.WriteLine($"k=12 result={maxDiff(root, 12)} expected=9");
}