Create tarjan-algorithm.py

graph/tarjan-algorithm.py

@@ -0,0 +1,118 @@
+from collections import defaultdict 
+class Graph: 
+
+	def __init__(self,vertices): 
+		self.V= vertices 
+
+		self.graph = defaultdict(list) 
+
+		self.Time = 0
+
+	def addEdge(self,u,v): 
+		self.graph[u].append(v) 
+
+	def SCCUtil(self,u, low, disc, stackMember, st): 
+
+		disc[u] = self.Time 
+		low[u] = self.Time 
+		self.Time += 1
+		stackMember[u] = True
+		st.append(u) 
+
+		for v in self.graph[u]: 
+
+			if disc[v] == -1 : 
+
+				self.SCCUtil(v, low, disc, stackMember, st) 
+
+				low[u] = min(low[u], low[v]) 
+
+			elif stackMember[v] == True: 
+
+				low[u] = min(low[u], disc[v]) 
+
+		w = -1 #To store stack extracted vertices 
+		if low[u] == disc[u]: 
+			while w != u: 
+				w = st.pop() 
+				print w, 
+				stackMember[w] = False
+
+			print"" 
+
+	def SCC(self): 
+
+		disc = [-1] * (self.V) 
+		low = [-1] * (self.V) 
+		stackMember = [False] * (self.V) 
+		st =[] 
+
+		for i in range(self.V): 
+			if disc[i] == -1: 
+				self.SCCUtil(i, low, disc, stackMember, st) 
+
+
+
+
+
+# Create a graph given in the above diagram 
+g1 = Graph(5) 
+g1.addEdge(1, 0) 
+g1.addEdge(0, 2) 
+g1.addEdge(2, 1) 
+g1.addEdge(0, 3) 
+g1.addEdge(3, 4) 
+print "SSC in first graph "
+g1.SCC() 
+
+g2 = Graph(4) 
+g2.addEdge(0, 1) 
+g2.addEdge(1, 2) 
+g2.addEdge(2, 3) 
+print "nSSC in second graph "
+g2.SCC() 
+
+
+g3 = Graph(7) 
+g3.addEdge(0, 1) 
+g3.addEdge(1, 2) 
+g3.addEdge(2, 0) 
+g3.addEdge(1, 3) 
+g3.addEdge(1, 4) 
+g3.addEdge(1, 6) 
+g3.addEdge(3, 5) 
+g3.addEdge(4, 5) 
+print "nSSC in third graph "
+g3.SCC() 
+
+g4 = Graph(11) 
+g4.addEdge(0, 1) 
+g4.addEdge(0, 3) 
+g4.addEdge(1, 2) 
+g4.addEdge(1, 4) 
+g4.addEdge(2, 0) 
+g4.addEdge(2, 6) 
+g4.addEdge(3, 2) 
+g4.addEdge(4, 5) 
+g4.addEdge(4, 6) 
+g4.addEdge(5, 6) 
+g4.addEdge(5, 7) 
+g4.addEdge(5, 8) 
+g4.addEdge(5, 9) 
+g4.addEdge(6, 4) 
+g4.addEdge(7, 9) 
+g4.addEdge(8, 9) 
+g4.addEdge(9, 8) 
+print "nSSC in fourth graph "
+g4.SCC(); 
+
+
+g5 = Graph (5) 
+g5.addEdge(0, 1) 
+g5.addEdge(1, 2) 
+g5.addEdge(2, 3) 
+g5.addEdge(2, 4) 
+g5.addEdge(3, 0) 
+g5.addEdge(4, 2) 
+print "nSSC in fifth graph "
+g5.SCC();