Check out example codes for "bfs". It will help you in understanding the concepts better.

Code Example 1

``````// Program to print BFS traversal from a given
// source vertex. BFS(int s) traverses vertices
// reachable from s.
#include<iostream>
#include <list>

using namespace std;

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

// Pointer to an array containing adjacency
// lists
public:
Graph(int V);  // Constructor

// function to add an edge to graph

// prints BFS traversal from a given source s
void BFS(int s);
};

Graph::Graph(int V)
{
this->V = V;
}

{
}

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
{
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);

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

return 0;
}``````

Code Example 2

``````procedure BFS(G, start_v) is
2      let Q be a queue
3      label start_v as discovered
4      Q.enqueue(start_v)
5      while Q is not empty do
6          v := Q.dequeue()
7          if v is the goal then
8              return v
9          for all edges from v to w in G.adjacentEdges(v) do
10             if w is not labeled as discovered then
11                 label w as discovered
12                 w.parent := v
13                 Q.enqueue(w)``````

Code Example 3

``````function breadthFirstSearch (Start, Goal)
{
enqueue(Queue,Start)
setVisited(start)
while notEmpty(Queue)
{
Node := dequeue(Queue)
if Node = Goal
{
return Node
}
for each Child in Expand(Node)
{
if notVisited(Child)
{
setVisited(Child)
enqueue(Queue, Child)
}
}
}
}``````

Code Example 4

``````function breadthFirstSearch (Start, Goal)
{
enqueue(Queue,Start)
setVisited(start)
while notEmpty(Queue)
{
Node := dequeue(Queue)
if Node = Goal
{
return Node
}
for each Child in Expand(Node)
{
if notVisited(Child)
{
setVisited(Child)
enqueue(Queue, Child)
}
}
}
}``````

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