Iterative Depth First Traversal of Graph

https://www.geeksforgeeks.org/iterative-depth-first-traversal/

// An Iterative C++ program to do DFS traversal from
// a given source vertex. DFS(int s) traverses vertices
// reachable from s.
#include<bits/stdc++.h>
using namespace std;

// This class represents a directed graph using adjacency
// list representation
class Graph
{
    int V;    // No. of vertices
    list<int> *adj;    // adjacency lists
public:
    Graph(int V);  // Constructor
    void addEdge(int v, int w); // to add an edge to graph
    void DFS(int s);  // prints all vertices in DFS manner
    // from a given source.
};

Graph::Graph(int V)
{
    this->V = V;
    adj = new list<int>[V];
}

void Graph::addEdge(int v, int w)
{
    adj[v].push_back(w); // Add w to v’s list.
}

// prints all not yet visited vertices reachable from s
void Graph::DFS(int s)
{
    // Initially mark all verices as not visited
    vector<bool> visited(V, false);

    // Create a stack for DFS
    stack<int> stack;

    // Push the current source node.
    stack.push(s);

    while (!stack.empty())
    {
        // Pop a vertex from stack and print it
        s = stack.top();
        stack.pop();

        // Stack may contain same vertex twice. So
        // we need to print the popped item only
        // if it is not visited.
        if (!visited[s])
        {
            cout << s << " ";
            visited[s] = true;
        }

        // Get all adjacent vertices of the popped vertex s
        // If a adjacent has not been visited, then puah it
        // to the stack.
        for (auto i = adj[s].begin(); i != adj[s].end(); ++i)
            if (!visited[*i])
                stack.push(*i);
    }
}

// Driver program to test methods of graph class
int main()
{
    Graph g(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);

    cout << "Following is Depth First Traversal\n";
    g.DFS(0);

    return 0;
}

DFS Recursive

https://www.geeksforgeeks.org/depth-first-search-or-dfs-for-a-graph/

// C++ program to print DFS traversal from
// a given vertex in a  given graph
#include<iostream>
#include<list>
using namespace std;

// Graph class represents a directed graph
// using adjacency list representation
class Graph
{
    int V;    // No. of vertices

    // Pointer to an array containing
    // adjacency lists
    list<int> *adj;

    // A recursive function used by DFS
    void DFSUtil(int v, bool visited[]);
public:
    Graph(int V);   // Constructor

    // function to add an edge to graph
    void addEdge(int v, int w);

    // DFS traversal of the vertices
    // reachable from v
    void DFS(int v);
};

Graph::Graph(int V)
{
    this->V = V;
    adj = new list<int>[V];
}

void Graph::addEdge(int v, int w)
{
    adj[v].push_back(w); // Add w to v’s list.
}

void Graph::DFSUtil(int v, bool visited[])
{
    // Mark the current node as visited and
    // print it
    visited[v] = true;
    cout << v << " ";

    // Recur for all the vertices adjacent
    // to this vertex
    list<int>::iterator i;
    for (i = adj[v].begin(); i != adj[v].end(); ++i)
        if (!visited[*i])
            DFSUtil(*i, visited);
}

// DFS traversal of the vertices reachable from v.
// It uses recursive DFSUtil()
void Graph::DFS(int v)
{
    // Mark all the vertices as not visited
    bool *visited = new bool[V];
    for (int i = 0; i < V; i++)
        visited[i] = false;

    // Call the recursive helper function
    // to print DFS traversal
    DFSUtil(v, visited);
}

int main()
{
    // Create a graph given in the above diagram
    Graph g(4);
    g.addEdge(0, 1);
    g.addEdge(0, 2);
    g.addEdge(1, 2);
    g.addEdge(2, 0);
    g.addEdge(2, 3);
    g.addEdge(3, 3);

    cout << "Following is Depth First Traversal"
            " (starting from vertex 2) \n";
    g.DFS(2);

    return 0;
}