# requires python3.6 or above
# requires networkx, matplotlib
import numpy as np
import networkx as nx
import matplotlib as plt

def all_cycles_k_recursive(G, source, k, current_node, visited, cycle, allcycles):
    """
    """
    # mark current node as visited
    visited[current_node] = True
    cycle.append(current_node)
    
    if k == 1:
        # maximum length achieved
        if G[current_node][source] == 1:
            print(cycle)
            allcycles.append(cycle[:])
            
    else:
        for item in np.nonzero(G[current_node])[0]:
            if visited[item] == False:
                all_cycles_k_recursive(G, source, k-1, item, visited, cycle, allcycles)
            
    visited[current_node] = False
    cycle.pop() # make the current node available
        
    
    

def all_cycles_k(G, source, k):
    """
    G: numpy adj array with element i,j == 1 if there's a connection from i to j (transpose of the conventional adj mat) 
    source: source node, int number
    k: length of the cycles, int number
    """
    
    allcycles = []
    visited = [False] * np.max(G.shape)
    cycle = [] # current cycle
    #cycle.append(source)
    
    all_cycles_k_recursive(G, source, k-1, source, visited, cycle, allcycles)
    
    return allcycles