BFS

#include<iostream>
#include<bits/stdc++.h>
using namespace std;

class Graph{
    public:
    int vertex;
    list<int>* adjacent;
    bool *vertices;
    Graph(int t)
    {
        vertex=t;
        adjacent=new list<int>[t];
        vertices=new bool[t];
    }
    void addEdge(int source,int destination)
    {
        adjacent[source].push_back(destination);
        adjacent[destination].push_back(source);
    }
    void Breadth_first_search(int start)
    {
        int i;
        for(i=0;i<vertex;i++)
        vertices[i]=false;
        
        queue<int> q;
        
        vertices[start]=true;
        
        q.push(start);
        
        list<int>::iterator j;
        
       // cout<<start<<"->";
        
        while(!q.empty())
        {
            int curr_vertex=q.front();
            
            cout<<q.front()<<" ";
            
            vertices[curr_vertex]=true;
            
            
            
            //cout<<curr_vertex<<"->";
            
            q.pop();
            
            /*if(q.empty())
            cout<<"yes"<<" ";
            else
            cout<<"no"<<" ";*/
            
            for(j=adjacent[curr_vertex].begin();j!=adjacent[curr_vertex].end();j++)
            {
                int present_vertex=*j;
                if(!vertices[present_vertex])
                {
                    vertices[present_vertex]=true;
                    q.push(present_vertex);
                }
            }
        }
    }
    
};


int main()
{
    Graph g(4);
    
    g.addEdge(0,1);
    g.addEdge(0,2);
    g.addEdge(1,2);
    g.addEdge(2,3);
    //g.addEdge(3,3);
    
    g.Breadth_first_search(2);
}