I´m getting NZEC error in multiple submisions by changing a little bit the code below, the idea in general of the algorithm is checking if the Graph in bipartite or not by using BFS and bicoloring the nodes, I´ve already make google research trying to figure out the reasons of NZEC but i´m stuck, on my computer works fine
import sys
def make_link(G, n1, n2):
if u not in G:
G[n1] = []
if v not in G:
G[n2] = []
G[n1].append(n2)
G[n2].append(n1)
def bfs(G, root):
q = [root]
color = [-1] * (len(G.keys()) + 1)
color[root] = 1
while q:
v = q.pop(0)
for nb in G[v]:
checked[nb] = 1
if color[nb] == -1:
color[nb] = 1 - color[v]
q.append(nb)
elif color[nb] == color[v]:
return False
return True
n = int(sys.stdin.readline())
for i in xrange(n):
print 'Scenario #' + str(i + 1) + ':'
G = {}
b, c = map(int, sys.stdin.readline().split())
checked=[0]*(b+1)
for j in xrange(c):
u, v = map(int, sys.stdin.readline().split())
make_link(G, u, v)
for k in xrange(b):
if checked[k+1]==0:
s=bfs(G,k+1)
if s==False:
print 'Suspicious bugs found!'
break
if s==True:
print 'No suspicious bugs found!'
