bipartite graph.cpp

#include <iostream>
#include<list>
#include<queue>
using namespace std;


class Graph{
    
    int V;
    list<int> *l;
    
    public:
        Graph(int v){
            V = v;
            l = new list<int>[V];
            
        }
        
        void addEdge(int u,int v){
            l[u].push_back(v);
            l[v].push_back(u);
        }
        
        
        bool isBipartite(int s){
            
            queue<int> q;
            q.push(s);
            
            int *colors = new int[V];
            for(int i=0;i<V;i++){
                colors[i] = -1; //Not Visited
            }
            
            colors[s] = 0;
            bool ans = true;
            
            while(!q.empty() && ans){
                
                int u = q.front();
                q.pop();
                
                for(auto v:l[u]){
                    
                    if(colors[v]==-1){
                        colors[v] = 1 - colors[u];
                        q.push(v);
                    }
                    else if(colors[v]==colors[u]){
                        return false;
                    }   
                }   
            }       
        return true;
        }    
};

int main() {
    Graph g(4);
    g.addEdge(0,1);
    g.addEdge(2,0);
    g.addEdge(1,3);
    g.addEdge(2,3);
    g.addEdge(0,3);
    
    if(g.isBipartite(0)){
        cout<<"Yes it is";
    }
    else{
        cout<<"No it is not";
    }
}