public static Node GetLowestCommonAncestor(Node root, Node p, Node q)
{
AncestryResult r = GetLowestCommonAncestorHelper(root, p, q);
if (r.IsAncestor)
{
return(r.Node);
}
return(null);
}
public static AncestryResult GetLowestCommonAncestorHelper(Node root, Node p, Node q)
{
if (root == null)
{
return(new AncestryResult(null, false));
}
if (root == p && root == q)
{
return(new AncestryResult(root, true));
}
AncestryResult rX = GetLowestCommonAncestorHelper(root.Left, p, q);
if (rX.IsAncestor)
{
return(rX);
}
AncestryResult rY = GetLowestCommonAncestorHelper(root.Right, p, q);
if (rY.IsAncestor)
{
return(rY);
}
if (rX.Node != null && rY.Node != null)
{
return(new AncestryResult(root, true));
}
else if (root == p || root == q)
{
bool isAncestor = rX.Node != null || rY.Node != null;
return(new AncestryResult(root, isAncestor));
}
else
{
return(new AncestryResult(rX.Node != null ? rX.Node : rY.Node, false));
}
}
