undirected graph(connected/not)

#include<iostream>
using namespace std;
int adj[100][100],v,time;
int color[100];
void DFS_Visit(int u);
void DFS()
{
	for(int i=1;i<=v;i++)
	{
	    time++;

		color[i]=0;


			DFS_Visit(i);
	}
}
void DFS_Visit(int u)
{
	color[u]=1;

	for(int i=1;i<=v;i++)
		{
            		int k=adj[u][i];
            		if(k==1&&color[i]==0)
            		{
            			DFS_Visit(i);
            		}
		}
            		color[u]=2;

}

int main()
{
	int a,b,k=1;
	cout<<"Input Vertex Number :";
	cin>>v;
	k=1;
	do
	{
		cout<<"Edge "<<k<<" : ";
		cin>>a>>b;
		if( a>v || b>v)
		{
			cout<<"Invalid Input,try again... "<<endl;
		}
		else if(a<=0 || b<=0)
        {

            break;
        }
		else
		{
			adj[a][b]=1;
			adj[b][a]=1;
			k++;
		}
	}while(a!=0 && b!=0);



	DFS();
	if(time==v)
    {
        cout<<"connected"<<endl;

    }
    else{
        cout<<"Not connected";
    }
}