查找到树中任何节点的距离

Question

I am trying to get the depth of the node from other nodes in the following tree. I have a list with the parent-child relationship:

Parent -> Children

[2] -> [0]

[1] -> [2,5]

[5] -> [3,4,6]

I want to find the depth/distance of one node from other nodes. So, from node [5] , the depth[]={3,1,2,1,1,0,1}

I currently have:

def get_depth(self,idx,depth):

        self.depth[idx]=depth
        for child in self.sentence_prop.words[idx].children:
            get_depth(child[0],depth+1)
        return

where idx= [5] and initial depth=0 . I did this only for the child but I am not sure how to do it for parent.

Answer 1

I hope this solves your problem.

1) The distance between 2 nodes is given by this formulae:

Dist(n1, n2) = Dist(root, n1) + Dist(root, n2) - 2*Dist(root, lca)

Here lca : Lowest common ancestor of n1 and n2. This works in any general tree.

2) What you need to do:

1. Store paths corresponding to each node you want to find distance of
2. Iterate through the paths to find the common path length.
3. return (len(path1)+len(path2)-2*(common_path_length))

The implementation of this concept for a binary tree is here