Python/Graphs/KahnsAlgorithm_topo.py
2018-10-02 21:02:25 +05:30

33 lines
761 B
Python

# Kahn's Algorithm is used to find Topological ordering of Directed Acyclic Graph using BFS
def topologicalSort(l):
indegree = [0] * len(l)
queue = []
topo = []
cnt = 0
for key, values in l.items():
for i in values:
indegree[i] += 1
for i in range(len(indegree)):
if indegree[i] == 0:
queue.append(i)
while(queue):
vertex = queue.pop(0)
cnt += 1
topo.append(vertex)
for x in l[vertex]:
indegree[x] -= 1
if indegree[x] == 0:
queue.append(x)
if cnt != len(l):
print("Cycle exists")
else:
print(topo)
# Adjacency List of Graph
l = {0:[1,2], 1:[3], 2:[3], 3:[4,5], 4:[], 5:[]}
topologicalSort(l)