How could I change this Python code to Matlab?

This is python code. I want to write this code in matlab. is there any tools for that?

# Python program to detect cycle  
# in a graph 
  
from collections import defaultdict 
  
class Graph(): 
    def __init__(self,vertices): 
        self.graph = defaultdict(list) 
        self.V = vertices 
  
    def addEdge(self,u,v): 
        self.graph[u].append(v) 
  
    def isCyclicUtil(self, v, visited, recStack): 
  
        # Mark current node as visited and  
        # adds to recursion stack 
        visited[v] = True
        recStack[v] = True
  
        # Recur for all neighbours 
        # if any neighbour is visited and in  
        # recStack then graph is cyclic 
        for neighbour in self.graph[v]: 
            if visited[neighbour] == False: 
                if self.isCyclicUtil(neighbour, visited, recStack) == True: 
                    return True
            elif recStack[neighbour] == True: 
                return True
  
        # The node needs to be poped from  
        # recursion stack before function ends 
        recStack[v] = False
        return False
  
    # Returns true if graph is cyclic else false 
    def isCyclic(self): 
        visited = [False] * self.V 
        recStack = [False] * self.V 
        for node in range(self.V): 
            if visited[node] == False: 
                if self.isCyclicUtil(node,visited,recStack) == True: 
                    return True
        return False
  
g = Graph(4) 
g.addEdge(0, 1) 
g.addEdge(0, 2) 
g.addEdge(1, 2) 
g.addEdge(2, 0) 
g.addEdge(2, 3) 
g.addEdge(3, 3) 
if g.isCyclic() == 1: 
    print "Graph has a cycle"
else: 
    print "Graph has no cycle"
  
# Thanks to Divyanshu Mehta for contributing this code 

[Rik]

I don't know of any automatic tools to convert Python to Matlab, but you can call Python from Matlab and the reverse.

Answer 1

[Guillaume]

As Rik says there's no tool to convert python code into matlab so you'd have to do that manually, first by understanding what the python code is doing, then by writing the equivalent in matlab.

Of course, if you don't know what the python code is doing you have a problem. (But why are you using code your don't understand?)

Saying that, the code you show is trivially converted into matlab since matlab has built-in classes for graphs. The particular code shown is for a directed graph, digraph in matlab, so:

g = digraph;
g = addedge(g, 0, 1);
g = addedge(g, 0, 2); 
g = addedge(g, 1, 2);
g = addedge(g, 2, 0);
g = addedge(g, 2, 3);
g = addedge(g, 3, 3);
g.isdag      %is graph directly acyclic or not?

edit: stupid autocorrect inserted the wrong words

[NA]

In my case I only have edge of graph.

E=[1 2;1 5;2 3;2 4;2 5;3 4;4 5;4 7;4 9;5 6;6 11;6 12;6 13; 7 8;7 9;9 10;9 14;10 11;12 13;13 14];

I want to find cycle of graph using DFS. I know how DFS works.

As matlab does not have built-in DFS code. I found thw above code in Python.

So I think if I can change it to matlab code, I can find a cycle

[Guillaume]

"As matlab does not have built-in DFS"

If you'd followed the link to digraph I've posted in my answer, you would have seen in the list of functions dfsearch.

With your E matrix the graph can be trivially constructed:

g = digraph(E(:, 1), E(:, 2))

[Sean de Wolski]

This is the right answer. One of the key reasons to use MATLAB is for MathWorks developed and tested software. There's no reason to reinvent the wheel here unless this is a homework assignment.

[NA]

I mean ''There are no built-in algorithms in matlab to find cycles in graphs''.

I also find this DFS but do not know how to change it to find cycle

So, I tried to write my own code but have a problem. Finally I found this Python code, but do not understand it.

[Guillaume]

As I said if you want to know if a directed graph has cycles, use isdag. It will return true if there's no cycle and false otherwise. No need to write your own code.

[NA]

Sorry, I mean I want to find all cycle in graph using DFS. Not only reture, true or fulse

in my case I want to print out , [1,2,5],[1,2,4,5],[2,3,4],....

[Guillaume]

This has actually been answered recently, See this post for a simple solution.