Solution: Depth-First Graph Traversal

def dfs(my_graph, source):
    """
    Function to print a DFS of graph
    :param graph: The graph
    :param source: starting vertex
    :return: returns the traversal in a string
    """
    
    # Mark all the vertices as not visited
    visited = [False] * (len(my_graph.graph))
    # Create a stack for DFS
    stack = []
    # Result string
    result = ""
    # Push the source
    stack.append(source)
    while stack:
        # Pop a vertex from stack
        source = stack.pop()
        
        if not visited[source]:
            result += str(source)
            visited[source] = True
        # Get all adjacent vertices of the popped vertex source.
        # If a adjacent has not been visited, then push it
        while my_graph.graph[source] is not None:
            data = my_graph.graph[source].vertex
            if not visited[data]:
                stack.append(data)
            my_graph.graph[source] = my_graph.graph[source].next
    return result
# Main to test the above program
if __name__ == "__main__":
    
    V = 5
    g = Graph(V)
    g.add_edge(0, 1)
    g.add_edge(0, 2)
    g.add_edge(1, 3)
    g.add_edge(1, 4)
    print(dfs(g, 0))