From 6ae119a40b7ee9021e29e37903aec904ced3fa49 Mon Sep 17 00:00:00 2001
From: Eryk Miszczuk <erymis@st.amu.edu.pl>
Date: Fri, 13 Dec 2019 15:01:42 +0100
Subject: [PATCH] Return immediately if edge starts and finishes in the same
 node

---
 TaskB05/run.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/TaskB05/run.py b/TaskB05/run.py
index 440c8d2..a13bcae 100644
--- a/TaskB05/run.py
+++ b/TaskB05/run.py
@@ -26,6 +26,9 @@ def dfs(graph, start):
     while stack:
         edge = stack.pop()
         #print('Current edge: {edge}'.format(edge = edge))
+        #return immediately if cycle is detected
+        if edge[0] == edge[2]:
+            return [-1]
         if edge not in visited:
             visited.add(edge)
             children = set()
@@ -37,7 +40,7 @@ def dfs(graph, start):
             return [-1]
     return visited
     
-
+# load atand format from stdin
 for line in sys.stdin:
     line = line.replace('\n', '')
     move = atandt_desc_pattern.match(line)