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# Check whether Graph is Bipartite or Not using BFS
# A Bipartite Graph is a graph whose vertices can be divided into two independent sets,
# U and V such that every edge (u, v) either connects a vertex from U to V or a vertex
# from V to U. In other words, for every edge (u, v), either u belongs to U and v to V,
# or u belongs to V and v to U. We can also say that there is no edge that connects
# vertices of same set.
def checkBipartite(l):
queue = []
visited = [False] * len(l)
color = [-1] * len(l)
def bfs():
while queue:
u = queue.pop(0)
visited[u] = True
for neighbour in l[u]:
if neighbour == u:
return False
if color[neighbour] == -1:
color[neighbour] = 1 - color[u]
queue.append(neighbour)
elif color[neighbour] == color[u]:
return False
return True
for i in range(len(l)):
if not visited[i]:
queue.append(i)
color[i] = 0
if bfs() == False:
return False
return True
# Adjacency List of graph
l = {0: [1, 3], 1: [0, 2], 2: [1, 3], 3: [0, 2]}
print(checkBipartite(l))