find parent of each node

[afrooze]

Hi. can you explain to me how can find a common parent for each node?

[yuvalshi0]

I used the node predecessor to iterate over the tree nodes, starting from the leaf to the root:

node = tree.get_node(node_id)
    while node.predecessor:
        if your_condition:
            return node.identifier
        node = tree[node.predecessor]

[jmount1992]

An alternative answer to @yuvalshi0 is:

1. Get the depth of the two nodes
2. Start at the deeper of the two nodes, and keep going up until at the same depth as the other node
3. When at the same depth, if the nodes are not the same, then continue moving both up one parent and check if they are the same node

Execution time will depend on the depth of desired nodes. There are better alternatives out there. Search lower common ancestor graph as a start.

Example function

def get_common_frame(tree, node_1: str, node_2: str) -> str:
        """gets the lowest common ancester between two nodes.

        Args:
            tree: treelib tree object
            node_1 (str): the ID of the first node (first and second has no meaning)
            node_2 (str): the ID of the second node

        Returns:
            str: the identifier of the lowest common ancestor node
        """

        # check to see which node is deeper
        if tree.depth(node_1) > tree.depth(node_1):
            # node 1 is further down tree
            lower_node = node_1
            higher_node = node_2
        else:
            # node 2 is further down tree
            lower_node = node_2
            higher_node = node_1

        # go until lower node has same depth as higher node
        while tree.depth(lower_node) != tree.depth(higher_node):
            lower_node = tree.parent(lower_node).identifier

        # move both up one level until lower node equals higher node
        while lower_node != higher_node:
            lower_node = tree.parent(lower_node).identifier
            higher_node = tree.parent(higher_node).identifier

        # return
        return lower_node

Edited: To improve clarity

[afrooze]

thanks for answers