adjacency-list

问题 I've just started learning about graphs, and something that's confusing me is why we need to use external data structures (like matrices or lists) to store which vertexes of the graph are connected to other vertices. Why can't each vertex just hold references to the vertices its connected to, like the way nodes do in a decision tree? That, to me, seems more intuitive. Thanks! 回答1: Well, this comes from a design philosophy. Whenever you have a many to many relationships, you introduce a broker

问题 I am searching for an efficient solution to build a secondary in-memory index in Python using a high-level optimised mathematical package such as numpy and arrow. I am excluding pandas for performance reasons. Definition "A secondary index contains an entry for each existing value of the attribute to be indexed. This entry can be seen as a key/value pair with the attribute value as key and as value a list of pointers to all records in the base table that have this value." - JV. D'Silva et al.

问题 I'm trying to get ancestors of a child (dog) upto Level 5. For Example in attached picture I'll be sending "Spencer di Casa Massarelli" and in result want to have associated parents (both father and mother). In my DB structure I've used father_id and mother_id. DB & version: 10.4.11-MariaDB Table Script: CREATE TABLE `dogs` ( `dog_id` int(11) NOT NULL, `name` varchar(255) DEFAULT NULL, `father_id` int(11) DEFAULT NULL, `moter_id` int(11) DEFAULT NULL, PRIMARY KEY (`dog_id`) ) ENGINE=InnoDB

问题 Is there any effective way to, without limiting the depth, retrieve a single path in a Adjacency List model based on the node's ID? Like if I've got an ID for a node named "Banana" I could get the following Path: Food > Fruits > Banana It's not a big problem if it's impossible, but I thought about if it could be possible to run joins through a while-loop or something? Until the parent turns 0. 回答1: No, not in MySQL at least. That is one of the biggest limitations of the Adjacency List Model.

问题 So I have a graph in the form of an adjacency list, structured as in the code below. Given this form of a data structure, I was wondering how it would be possible to go about finding and printing all the possible paths from a given node to another node. I'm aware I might have to used stacks to perform a DFS or queues to perform BFS, which I know how to do, but am confused by how to find all the possible paths typedef struct graph { int n, maxn; Vertex** vertices; }Graph; typedef struct vertex

问题 In C#, I have class Pair{ int val1; int val2; } I have a list of pairs coming from a source as:- List<Pair> sList = new List<Pair>(); 1 | 2 2 | 3 1 | 4 4 | 6 I need to convert it into the following type of structure:- [1, [2, 3, 4, 6]] [2, [3]] [3, [2]] [4, [1,6]] [6, [4]] What is the best way to go about this (without LINQ)? 回答1: I would go with an ILookup<int, int> , but you need to include the reverse associations as well: var result = sList.Union(sList.Select(p => new Pair { val1 = p.val2

问题 Sorry for my inexperience with C++, but I spent quiet some time with solving a cyclic dependency issue and hence posing this. I am trying to represent a Adjacency List in C++. I have struct Node , struct Node{ int data; unordered_set<Node, Hash> links; bool operator == (Node const& other) const{ return (data == other.data); } Node(){ } Node(int data){ this->data = data; } }; and I have my Hash functor struct Hash { size_t operator()(const Node &node) const { return node.data; }; }; I noticed

问题 I was playing around (out of interest) with retrieving a tree of nodes in a simple adjacency list with a recursive query using local variables. The solution i have so far is fun but i wonder (and this is my only question) why MySQL refuses to use any INDEX to optimize this query. Shouldn't MySQL be able to lookup the nearest child(s) by using an INDEX ? I'm curious why MySQL doesn't. Even when i use FORCE INDEX the execution plan doesn't change. This is the query so far, with 5 being the ID

问题 I have a table in my database where I store a tree structure using the hybrid Nested Set (MPTT) model (the one which has lft and rght values) and the Adjacency List model (storing parent_id on each node). my_table (id, parent_id, lft, rght, alias) This question doesn't relate to any of the MPTT aspects of the tree but I thought I'd leave it in in case anyone had a good idea about how to leverage that. I want to convert a path of aliases to a specific node. For example: "users.admins.nickf"

问题 Context I am building a forum and investigating modeling the data with DynamoDB and adjacency lists. Some top-level entities (like users) might have multiple types of relationships with other top-level entities (like comments). Requirements For example, let's say we want be able to do the following: Users can like comments Users can follow comments Comments can display users that like it Comments can display users that follow it User profiles can show comments they like User profiles can show