BFS using vectors & queue as per the algorithm of CLRS

using System;
using System.Collections.Generic;

namespace GraphTraversal {
  public class Graph {
    private int V;
    private List<int>[] g;

    // Declaring the arrays to store color, distance
    // and parent
    string[] colour;
    int[] d, p;

    // Constructor
    Graph(int v)
    {
      V = v;
      g = new List<int>[ v ];
      for (int i = 0; i < v; i++)
        g[i] = new List<int>();
    }

    // Function to add an edge into the graph
    void addEdge(int u, int v)
    {
      g[u].Add(v);
      g[v].Add(u);
    }

    // This function does the Breadth First Search
    void BFSSingleSource(int s)
    {
      // The Queue used for the BFS operation
      Queue<int> q = new Queue<int>();

      // Pushing the root node inside the queue
      q.Enqueue(s);

      /* Distance of root node is 0 & colour
            is gray as it is visited partially now */
      d[s] = 0;
      colour[s] = "green";

      /* Loop to traverse the graph. Traversal
            will happen traverse until the queue is
            not empty.*/
      while (q.Count != 0) {
        /* Extracting the front element(node)
                and popping it out of queue. */
        int u = q.Dequeue();

        Console.Write(u + " ");

        /* This loop traverses all the child nodes of u
             */
        foreach(int i in g[u])
        {
          /* If the colour is white then the said node
                        is not traversed. */
          if (colour[i] == "white") {
            colour[i] = "green";
            d[i] = d[u] + 1;
            p[i] = u;

            /* Pushing the node inside queue
                            to traverse its children. */
            q.Enqueue(i);
          }
        }

        /* Now the node u is completely traversed
                and colour is changed to black. */
        colour[u] = "dark_green";
      }

      Console.WriteLine();
    }

    void BFSFull(int n)
    {
      /* Initially all nodes are not traversed.
            Therefore, the colour is white. */
      colour = new string[n];
      d = new int[n];
      p = new int[n];
      Array.Fill(colour, "white");
      Array.Fill(d, 0);
      Array.Fill(p, -1);

      // Calling BFSSingleSource() for all white
      // vertices.
      for (int i = 0; i < n; i++) {
        if (colour[i] == "white")
          BFSSingleSource(i);
      }
    }

    // Driver method
    static void Main(string[] args)
    {
      int n = 7;
      Graph g = new Graph(7);
      g.addEdge(0, 1);
      g.addEdge(0, 2);
      g.addEdge(1, 3);
      g.addEdge(1, 4);
      g.addEdge(2, 5);
      g.addEdge(2, 6);

      g.BFSFull(n);
    }
  }
}

// This code is contributed by ishankhandelwals.