def eulerian_cycle(G: DirectedGraphMatrix) -> list:
"""
Find eulerian cycle in the given graph
Args:
graph to find eulerian cycle in
Return:
path of the cycle if found or None if not found
"""
def selfloop(u: int):
nonlocal G
path = []
cur = u
while cur != u or not path:
path.append(cur)
(v, c) = G.adj(cur).__next__()
G.remove_edge(DirectedEdge(cur, v))
cur = v
path.append(u)
return path
G = deepcopy(G)
E = G.E()
tour = [0]
cur = 0
while cur < len(tour):
try:
G.adj(tour[cur]).__next__()
tour = tour[:cur] + selfloop(tour[cur]) + tour[cur + 1:]
except StopIteration:
cur += 1
return tour if len(tour) == E + 1 else None
#!/usr/bin/env python3
from common import IO
from graph.directed import Graph, GraphMatrix
from graph import algorithm
io = IO()
G = Graph.fromfile(io.filein)
G_matrix = GraphMatrix.from_graph(G)
# Eulerian cycle, part 1
io.section('Eulerian cycle')
eulerian_cycle = algorithm.eulerian_cycle(G_matrix)
if eulerian_cycle is not None:
io.print('Eulerian cycle found: ')
io.print_path(eulerian_cycle)
else:
io.print('Eulerian cycle not found!')
# Eulerian path, part 2
io.section('Eulerian path')
eulerian_path = algorithm.eulerian_path(G_matrix)
if eulerian_path is not None:
io.print('Eulerian path found: ')
io.print_path(eulerian_path)
else:
io.print('Eulerian path not found!')
# Hamiltonian cycle, part 1
io.section('Hamiltonian cycle')