Added ICPC-Referat

presentations/ICPC-Referat/Material/tarjans-short.py

@@ -0,0 +1,50 @@
+def strongly_connected_components(graph):
+	index_counter = 0
+	stack = []
+	lowlinks = {}
+	index = {}
+	result = []
+	
+	def strongconnect(node, index_counter):
+		index[node] = index_counter
+		lowlinks[node] = index_counter
+		index_counter += 1
+		stack.append(node)
+	
+		try:
+			successors = graph[node]
+		except:
+			successors = []
+
+		# Depth first search
+		for successor in successors:
+			# Does the current node point to a node that was already
+			# visited?
+			if successor not in lowlinks:
+				# Successor has not yet been visited; recurse on it
+				strongconnect(successor, index_counter)
+				lowlinks[node] = min(lowlinks[node],lowlinks[successor])
+			elif successor in stack:
+				# the successor is in the stack and hence in the 
+				# current strongly connected component (SCC)
+				lowlinks[node] = min(lowlinks[node],index[successor])
+		
+		# If `node` is a root node, pop the stack and generate an SCC
+		if lowlinks[node] == index[node]:
+			connected_component = []
+			
+			while True:
+				successor = stack.pop()
+				connected_component.append(successor)
+				if successor == node: break
+
+			component = tuple(connected_component)
+
+			# storing the result
+			result.append(component)
+	
+	for node in graph:
+		if node not in lowlinks:
+			strongconnect(node, index_counter)
+	
+	return result