public Enumerator(SmallDictionary <K, V> dict) : this()
{
var root = dict._root;
if (root != null)
{
// left == right only if both are nulls
if (root.Left == root.Right)
{
_next = root;
}
else
{
_stack = new Stack <AvlNode>(dict.HeightApprox());
_stack.Push(root);
}
}
}