Added very hard problem

Author: das-jishu

Very Hard/two-edge-connected-graph.py

@@ -0,0 +1,38 @@
+
+# TWO EDGE CONNECTED GRAPH
+
+# O(V + E) time and O(V) space
+def twoEdgeConnectedGraph(edges):
+    # Write your code here.
+    if len(edges) == 0:
+		return True
+	
+	arrivalTimes = [-1] * len(edges)
+	startVertex = 0
+	
+	if getMinTime(startVertex, -1, 0, arrivalTimes, edges) == -1:
+		return False
+	
+	return areAllVerticesVisited(arrivalTimes)
+
+def areAllVerticesVisited(arrivalTimes):
+	for time in arrivalTimes:
+		if time == -1:
+			return False
+		
+	return True
+
+def getMinTime(currentVertex, parent, currentTime, arrivalTimes, edges):
+	arrivalTimes[currentVertex] = currentTime
+	minimumArrivalTime = currentTime
+	
+	for destination in edges[currentVertex]:
+		if arrivalTimes[destination] == -1:
+			minimumArrivalTime = min(minimumArrivalTime, getMinTime(destination, currentVertex, currentTime + 1, arrivalTimes, edges))
+		elif destination != parent:
+			minimumArrivalTime = min(minimumArrivalTime, arrivalTimes[destination])
+		
+	if minimumArrivalTime == currentTime and parent != -1:
+		return -1
+	
+	return minimumArrivalTime