Python/graphs/scc_kosaraju.py
Caeden 4d0c830d2c
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Co-authored-by: Christian Clauss <cclauss@me.com>
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Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>
2022-10-13 18:03:06 +02:00

55 lines
1.3 KiB
Python

from __future__ import annotations
def dfs(u):
global graph, reversed_graph, scc, component, visit, stack
if visit[u]:
return
visit[u] = True
for v in graph[u]:
dfs(v)
stack.append(u)
def dfs2(u):
global graph, reversed_graph, scc, component, visit, stack
if visit[u]:
return
visit[u] = True
component.append(u)
for v in reversed_graph[u]:
dfs2(v)
def kosaraju():
global graph, reversed_graph, scc, component, visit, stack
for i in range(n):
dfs(i)
visit = [False] * n
for i in stack[::-1]:
if visit[i]:
continue
component = []
dfs2(i)
scc.append(component)
return scc
if __name__ == "__main__":
# n - no of nodes, m - no of edges
n, m = list(map(int, input().strip().split()))
graph: list[list[int]] = [[] for _ in range(n)] # graph
reversed_graph: list[list[int]] = [[] for i in range(n)] # reversed graph
# input graph data (edges)
for _ in range(m):
u, v = list(map(int, input().strip().split()))
graph[u].append(v)
reversed_graph[v].append(u)
stack: list[int] = []
visit: list[bool] = [False] * n
scc: list[int] = []
component: list[int] = []
print(kosaraju())