# Questions tagged [graph]

A graph is an abstract representation of objects (vertices) connected by links (edges). For questions about plotting data graphically, use the [data-visualization] tag instead.

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### Word ladders program in Python

Background information: Given two different strings of equal length, the spacing between them is the number of other strings you would need to connect them on a word ladder. Alternately, this is 1 ...
187 views

### Functional, recursive algorithm for flattening a tree

My goals for the algorithm were to use recursion, to avoid mutation, and to decouple the tree walking from the action that we take on each node. My sense is that the result uses mode code is ...
56 views

### Find the longest connect cells region per color

I have been studying graphs/BFS/DFS. working on wrapping my head around the following problem Given a grid [m,n] where each cell has a value denotes a color, find the longest connected region that ...
225 views

### Correctness of iterative DFS for cycle detection

I'm attempting the Graph Algorithms section in CLRS right now. Here's an iterative DFS using a stack called nodes. ...
180 views

### Graph library including minimum spanning tree using Kruskal's Algorithm

I've only ever made small programs. So, I've tried to make something large but easily reusable/extendable. Posted below are the beginnings of a graph library I've written up. One particular point I'd ...
287 views

### Factory for constructing directed graphs in C++

I want to implement a directed graph which has 3 main kind of edges: self referencing edges non directional edges between two nodes directional edges between two nodes Also I want to be able to do ...
54 views

### Using HashMaps to track parent and rank of graph nodes

I often find myself in the following position: I have created a class in some file, and would like to add a new data member to that class without changing the original class definition. Now, you ...
106 views

### Generate multi dimensional maze with borders and fixed degree on each node type

IMPORTANT: giving too big combination of node count and edge/neighbor count can overflow your RAM and swap file very quickly, thus I recommend staying below 500 on node count and below 50 on neighbor ...
34 views

### Modular graph searcher

some words in forehand: Unfortunately this post is very long, thus I decided to put the whole and compilable code into an online compiler. The link is at the end of this post. In the last few days I ...
2k views

### Greedy Graph Coloring in Python

Graph Coloring Algorithm (Greedy/ Welsh Powell) I am trying to learn graphs, and I couldn't find a Python implementation of the Welsh Powell algorithm online, so I tried to write my own. Here are the ...
176 views

### Implementing a faster inbound neighbour similarity in Networkx

Given a directed graph G of 20+ million edges and approximately 2 million unique nodes, can this function/process be made faster on a dataset of 40k edges? The current speed is at ~1.8 seconds per ...
211 views

### Displaying programming languages on a timeline

I did the following two exercises in Programming: Principles and Practice Using C++ (2nd Edition), by Stroustrup, which build upon each other: From Chapter 22 (Ideals and History), Write a ...
116 views

### Latitude/Longitude graph optimised A* Algorithm

Can anyone point me in the direction of a C# or pseudocode implementation of A* optimised for relatively sparsely connected graphs (average < 3 edges per node)? ...
318 views

### Dijkstra's algorithm in Rust

I'd love to get feedback on my first go at Dijkstra's algorithm in Rust: ...
306 views

### Adjacency list graph in Java

I am reading a text, that from a higher level explained adjacency list implementation of a graph. I have now tried to implement this as simply as I could. I did not see any reason to have an actual ...
84 views

### Making a graph of the import structure of a program

When I read other people's code, it's sometimes difficult to understand the import structure. I thought making a graph of the import structure of a given python program would be a fun programming task,...
255 views

### DFS for Graph search with generic data types

This question is a follow up to this. I am learning Graph data structure and have implemented DFS and BFS in a way that it can handle data types other than int. These function try to search an end or ...
49 views

### C++ - Graph implementation for data types other than int

I am learning graphs and most of the implementations that I see are meant for int. So, I decided to code an example that can take other data types such as ...
97 views

### Finding center of graph/tree

Given graph/network of nodes without any loops/circuits. I'm trying to find the center: the node from which I can reach all other nodes the fastest. Imagine if I want to spread the word about ...
118 views

### Finding intersting path in a graph

There is a question in a contest but it doesn't have any answer. I solve it but I get time limit for most of test case. Is it possible to improve my code or give a better approach? Question There is ...
90 views

Intro I've decided to learn haskell, because I've always enjoyed the functional aspect of Python and want to explore other languages that use this concept. I'm still stumbling in the dark most of the ...
120 views

### Maximize a traveling employee's vacation over k weeks

I have following problem statement A lazy employee works at a multi-national corporation with N offices spread across the globe. They want to work as few days over k weeks as possible. ...
271 views

### Python: Dijkstra's Algorithm

In this code, I focused more on code readability rather than algorithmic complexity. I didn't really care about the code in the main function because it was just ...
84 views

### A-Star Search with 3D Universe

I am attempting to write up a program in Python that will find the shortest path between two nodes in 3D space. The actual domain is the EVE-Online Universe, which is composed of systems connected by ...
65 views

### DFS logic to traverse a graph

I tried to literally convert recursive algorithm taught here to iterative, by simulating the recursive stack exactly as much as possible. I have tested my code and it passed all test cases. Please ...
3k views

### Searching a maze using DFS and BFS in Python 3

I solved the problem posted from Make School Trees and Maze article, which asks me to searching a maze using DFS and BFS in Python. Here's the final output from PyGame: I would like to ask for code ...
232 views

### Cracking the Coding Interview - 4.1 Graph Traversal

I'm working through the classic Cracking the Coding Interview book. I'm trying to solve the following graph problem: 4.1) Route Between Nodes: Given a directed graph, design an algorithm to find ...
103 views

### Building a graph using dictionary

I have an input text file which contains distance between 2 cities shown below ...
389 views

### Cycle in Directed graph to vector

I created a class of a directed graph and a method for finding if graph has an Euler cycle and updating a vector accordingly.Is there any optimization or a nicer way to do this. ...
108 views

### Add an edge to a graph to minimize the average shortest path length

This program is used to find the nodes in a grid network, between which, if an edge is added, the average shortest path length of the entire grid reduces by the most. "Average shortest path length" ...
273 views

### Greedy preference-matching algorithm

The problem that this is based on is something like the following: A matchmaker is working with six clients: John, Joe, Charlie, Jill, Leslie, and Katie. John is compatible with Jill and Leslie, ...
808 views

### Trace route based on Cisco routing table text output

I created a script for path search across network topology based on uploaded routing tables in text format. The final purpose is to be able to get all available paths to given subnet/host from each ...
787 views

### Milking order compatible with maximum number of observations

I'm using some old USA Computing Olympiad (USACO) problems to help teach me. This is the "Milking order" problem: Farmer John has $N$ cows ($1≤N≤10^5$), numbered $1…N$. He has made $M$ ...
272 views

### Balanced tree in C#

Given the adjacency list to represent a tree from the root (node 0) to the leaves, I want to write a function that takes this adjacency list as a parameter and return whether the tree is balanced. ...
174 views

### Draw common tangents to two circles interactively in MATLAB

Requirement After a user draws two circles with their mouse successively, the program should draw all common tangents, if any, to them. Here is my implementation ...
350 views

### Finding the size of the largest connected component in a graph

Given this question, which simply can be explained as follows: Given the number of nodes and the number of edges in a graph, find the size of the largest connected component of the graph. If this ...
1k views

### Graph Implementation in Java using adjacency list - v2

Updated version from Graph Implementation in Java using adjacency list ...
1k views

### Graph Implementation in Java using adjacency list

I am building a Graph class to learn and eventually plan to add Dijkstra's algorithm to this implementation. What do you think of the overall approach? Any feedback on how to improve this? Vertex....
382 views

### Max flow Ford-Fulkerson using DFS augmented path retrieval

I have written a naive max flow with DFS, could anyone review my below code. What can be done to improve the code and what are the worst cases where this won’t work acceptably? ...
1k views

### Depth First Search of graph in Python

Task: Do DFS traversal from a given given graph and print output. Is this code the correct implementation of DFS traversal in Graph? ...
72 views

### Djikstra implementation for large graphs

I am implementing the Djikstra algorithm for a large graph (40k nodes, 100k arcs). For shorter paths the searchtime is under a second for larger ones (from one end to the other) it take quite some ...
159 views

### Implement a graph in Python

Question : Build a graph in python, given its edge representation. ...
78 views

### Number of subGraphs with given vertice and degree

Demo: There are three questions: How many subgraphs whose Num(vertices) <= 5 and all vertices have two degrees? How many subgraphs whose Num(vertices) == 4 and all vertices have 3 degrees? If ...
346 views

### Player Marking , Optimal Marking Using Graph

I was asked this problem for a challenge, and I decided to share my solution here to review the code: Here is the problem statement: For this challenge, we are going to cover some graph problems. We ...
2k views

### Generic Graph using Adjacency matrix - Java

The main purpose of representing Graph using adjacency matrix method is, to check the vertex and its neighbor's existence in constant time proportional to $\mathcal{O}(n)$. In the various ...
198 views

### Java agent-based model

I've been working on an agent-based model as part of my PhD and I've hit a roadblock. I started learning Java by doing this project and I definitely started to run before I could walk. The problem is ...
825 views

### Graph Representation using smart pointers. Kosaraju's algorithm implementation

Coming from a Java background, and being fairly new to C++ as well as code review, I am trying to get accustomed to C++11/14 concepts. I have been reading Modern Effective C++ by Scott Meyers to ...
120 views

### Levenshtein Distance of transitively similar words

The code's purpose is this: Two words are friends if they have a Levenshtein distance of 1. That is, you can add, remove, or substitute exactly one letter in word X to create word Y. A word’s social ...
This is the Cheapest Flights Within K Stops problem from leetcode.com: There are $n$ cities connected by $m$ flights. Each fight starts from city $u$ and arrives at $v$ with a price $w$. ...