Data Structure in C++ Graphs and Breadth-first Search Adj. list graphs Write an

Question

Data Structure in C++

Graphs and Breadth-first Search

Adj. list graphs Write an implementation of the adjacency listgraph representation. You may assume that nodes are integers which start at 0. Using your implementation, implement the breadth-first-search algorithm, as a function which takes a graph a starting node and a target node, and searches for a path between them. Your BFS function should return the shortest distance from the source node to the target node, or -1 if no path exists. Commands Implement the following commands Command Description create nr Create a new empty graph in register r, with n nodes print r Print some representation of the graph in r arc a b r in the graph in register r, create an arc from node a to b biarc a b r Create a bidirectional arc from a to b in r bfs a b r Perform a breadth-first search from a to b in r, printing the distance Write the register commands necessary to create the following graph: and place them in a comment in your source code. What is the distance from node 9 to node 6?

Explanation / Answer

#include<iostream>
#include <list>

using namespace std;

// This class represents a directed graph using adjacency list representation
class Graph
{
int V; // No. of vertices
list<int> *adj; // Pointer to an array containing adjacency lists
public:
Graph(int V); // Constructor
void addEdge(int v, int w); // function to add an edge to graph
void BFS(int s);
};

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

void Graph::addEdge(int v, int w)
{
adj[v].push_back(w);
}

void Graph::BFS(int s)
{
// Mark all the vertices as not visited
bool *visited = new bool[V];
for(int i = 0; i < V; i++)
visited[i] = false;

// Create a queue for BFS
list<int> queue;

// Mark the current node as visited and enqueue it
visited[s] = true;
queue.push_back(s);

// 'i' will be used to get all adjacent vertices of a vertex
list<int>::iterator i;

while(!queue.empty())
{
// Dequeue a vertex from queue and print it
s = queue.front();
cout << s << " ";
queue.pop_front();

// Get all adjacent vertices of the dequeued vertex s
// If a adjacent has not been visited, then mark it visited
// and enqueue it
for(i = adj[s].begin(); i != adj[s].end(); ++i)
{
if(!visited[*i])
{
visited[*i] = true;
queue.push_back(*i);
}
}
}
}

// Driver program to test methods of graph class
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 Breadth First Traversal "
<< "(starting from vertex 2) ";
g.BFS(2);

return 0;
}

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