public T LowestCommonAncestor(T one, T two)
{
// we have several choices, either one of the values is the current (enabled) node, in which case the LCA is this value
if (_enabled && (_value.Equals(one) || _value.Equals(two)))
{
return(_value);
}
// if we've got here, then we know neither one nor two are equal to my value, unless this node is disabled
// else if both are to one side, then the LCA (if it exists) is that side
if (_left != null && _value.CompareTo(one) >= 0 && _value.CompareTo(two) >= 0)
{
return(_left.LowestCommonAncestor(one, two));
}
if (_right != null && _value.CompareTo(one) < 0 && _value.CompareTo(two) < 0)
{
return(_right.LowestCommonAncestor(one, two));
}
// else if they must be either side, then they need to be present on both sides
IList <T> both = new List <T> {
one, two
};
if (_left.Present(one) && _right.Present(two))
{
return(_value);
}
// otherwise there isn't one (i.e. either it would be this one and it is null or one or other of the values isn't present in the tree)
return(default(T));
}
public void TestLCA()
{
Assert.AreEqual(8, tree.LowestCommonAncestor(5, 9));
}