public static TreeBinaryParentNode <T> commonAncestor(TreeBinaryParentNode <T> firstNode, TreeBinaryParentNode <T> secondNode)
{
if (firstNode == null || secondNode == null)
{
throw new ArgumentNullException(message: "The nodes cannot be null", paramName: $"{nameof(firstNode)} or {nameof(secondNode)}");
}
int diff = getDepth(firstNode) - getDepth(secondNode);
TreeBinaryParentNode <T> deepNode = diff > 0 ? firstNode : secondNode;
TreeBinaryParentNode <T> swallowNode = diff > 0 ? secondNode : firstNode;
deepNode = goingUp(deepNode, Math.Abs(diff));
if (deepNode == swallowNode)
{
return(swallowNode);
}
while (swallowNode != null && deepNode != swallowNode)
{
deepNode = deepNode.parent;
swallowNode = swallowNode.parent;
}
return((swallowNode == null) ? null : swallowNode);
}
private static TreeBinaryParentNode <T> goingUp(TreeBinaryParentNode <T> node, int diff)
{
while (diff > 0)
{
node = node.parent;
diff--;
}
return(node);
}
private static int getDepth(TreeBinaryParentNode <T> node)
{
int depth = 0;
while (node.parent != null)
{
node = node.parent;
depth++;
}
return(depth);
}
private static TreeBinaryParentNode <T> MinimalParentTree <T>(T[] array, int start, int end, TreeBinaryParentNode <T> parent)
{
TreeBinaryParentNode <T> currentParent = parent;
if (start > end)
{
return(null);
}
int midIndex = (start + end) / 2;
T middle = array[midIndex];
parent = new TreeBinaryParentNode <T>(middle, null, null, currentParent);
parent.left = MinimalParentTree <T>(array, start, midIndex - 1, parent);
parent.right = MinimalParentTree <T>(array, midIndex + 1, end, parent);
return(parent);
}