UNDIRECTED GRAPHS (create, BFS, DFS, adjacent nodes)

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 BFS uses Queue and DFS uses Stack for implementation.

#include<bits/stdc++.h>
using namespace std;
int adj[15][15];
void dfs(int v, int n)
{
  //before Exploring the first node completely(push it to stack), 
  //move on to the exploration its of another connected node, 
  //if no node is connected or left further for exploration than pop from stack,
  //and print to visit that node.
  int stk[n],i,top=-1,visited[n+1]{0};
  top++;
  stk[top]=v;
  cout<<"DFS is : "<<v<<" ";
  visited[v]=1;
  while(top>=0)
  {
      v=stk[top];
      top-=1;
      if(visited[v]==0)
        {cout<<v<<" "; visited[v]=1;}
 
      for(i=1;i<=n;i++)
        if(adj[v][i]==1 && visited[i]==0)
      {top++;stk[top]=i;}
  }
}
void display(int n)
{
    int i,j;
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++)
        {cout<<adj[i][j]<<" ";}
        cout<<endl;

    }
}
void adjacent(int v, int n)
{
    int i;
    cout<<"\nAdjacent nodes are : ";
    for(i=1;i<=n;i++)
        if(adj[v][i]==1)
            cout<<i<<" ";
}
void bfs(int v, int n)
{
// First completely explore the ongoing node(add all its connected nodes to queue), 
//and than print that node to make it visited,
//Now pick up next node from queue(by moving front ahead),
// and explore it completely(push its connected nodes if not already present in queue), 
//now again print that node to make it visited and 
//move on to the next node until no node is left in the queue. 
     int qu[n], visited[n+1]{0}, frnt=-1, rear=-1, i;
     cout<<"BFS is : "<<v<<" ";
     visited[v]=1;
     rear++; frnt++;
     qu[rear]=v;
     while(frnt<=rear)
     {
         v=qu[frnt];
         frnt++;
         for(i=1;i<=n;i++) // checking unvisited nodes;
         {
             if(adj[v][i]==1 && visited[i]==0)
             {
                 cout<<i<<" ";
                 visited[i]=1;
                 rear++;
                 qu[rear]=i;
             }
         }
     }

}
void create(int n)
{
    int maxnodes=n*((n-1)/2),i,u,v,j;
    for(i=0;i<maxnodes;i++)
    {
        cout<<"\nOrigin & dest:(0,0 to exit): ";
        cin>>u>>v;
        if(u==0 && v==0)
            break;
        else if(  u> n || v > n || u<=0 || v<=0)
{
cout<<"Invalid edge!\n";
i--;
}
else
        {
            adj[u][v]=1;
            adj[v][u]=1;
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++)
        {cout<<adj[i][j]<<" ";}
        cout<<endl;

    }
}
int main()
{
    int n,i,j,vertex,choice,ch;
    cout<<"enter the number of nodes: ";
    cin>>n;
    create(n);

    while(ch)
    {
    cout<<"\nEnter 1. for BFS";
    cout<<"\nEnter 2. for DFS";
    cout<<"\nEnter 3. for adjacent nodes";
    cout<<"\nEnter 4. to display adjacency matrix";
    cout<<"\nEnter your choice";
    cin>>choice;
    if(choice==1)
    {
        cout<<"\nenter the starting vertex : ";
        cin>>vertex;
        bfs(vertex,n);
    }
    else if(choice==2)
    {
        cout<<"\nenter the starting vertex : ";
        cin>>vertex;
        dfs(vertex,n);
    }
    else if(choice==3)
    {
        cout<<"\nenter the vertex to find adjacent node : ";
        cin>>vertex;
        adjacent(vertex,n);
    }
    else if(choice==4)
    {
        display(n);
    }
    else
        cout<<"\nInvalid choice";

    cout<<"\nDo you want to continue(0 to exit) : ";
    cin>>ch;
    }
}

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