Iterative Depth First Traversal of Graph

Python/Iterative Depth First Traversal of Graph

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+# An Iterative Python program to do DFS traversal from 
+# a given source vertex. DFS(int s) traverses vertices 
+# reachable from s. 
+
+# This class represents a directed graph using adjacency 
+# list representation 
+class Graph: 
+ def __init__(self,V): # Constructor 
+ self.V = V # No. of vertices 
+ self.adj = [[] for i in range(V)] # adjacency lists 
+
+ def addEdge(self,v, w): # to add an edge to graph 
+ self.adj[v].append(w) # Add w to v’s list. 
+
+
+ # prints all not yet visited vertices reachable from s 
+ def DFS(self,s): # prints all vertices in DFS manner from a given source. 
+ # Initially mark all verices as not visited 
+ visited = [False for i in range(self.V)] 
+
+ # Create a stack for DFS 
+ stack = [] 
+
+ # Push the current source node. 
+ stack.append(s) 
+
+ while (len(stack)): 
+ # Pop a vertex from stack and print it 
+ s = stack[-1] 
+ stack.pop() 
+
+ # Stack may contain same vertex twice. So 
+ # we need to print the popped item only 
+ # if it is not visited. 
+ if (not visited[s]): 
+ print(s,end=' ') 
+ visited[s] = True
+
+ # Get all adjacent vertices of the popped vertex s 
+ # If a adjacent has not been visited, then push it 
+ # to the stack. 
+ for node in self.adj[s]: 
+ if (not visited[node]): 
+ stack.append(node) 
+
+
+
+# Driver program to test methods of graph class 
+
+g = Graph(5); # Total 5 vertices in graph 
+g.addEdge(1, 0); 
+g.addEdge(0, 2); 
+g.addEdge(2, 1); 
+g.addEdge(0, 3); 
+g.addEdge(1, 4); 
+
+print("Following is Depth First Traversal") 
+g.DFS(0) 
+
+# This code is contributed by Mehraj