Krdytkyu

there is my final code for implementing a Graph in C++ using adjacency list and Object-oriented. I got some help from StackOverflow and it was really helpful, but now I would ask about some advice for improving and a possible way of implementing two functions: isPath( v, w ) for finding if two nodes are connected and isConnected(graph) returning "yes" if the graph is strongly connected otherwise "no".

The code:

#include <iostream>

#include <vector>



using namespace std;



struct Edge {

    int source;

    int target;

};



class Graph

{

private:

    int numOfNodes;

    vector<vector<int>> baseVec;



public:

    Graph(int numOfNodes) : numOfNodes(numOfNodes), baseVec(numOfNodes) {}



    void newEdge(Edge edge) {

        if (edge.source >= numOfNodes || edge.target >= numOfNodes

            || edge.source < 0 || edge.target < 0) {

            cout << "Invalid edge!n";

            return;

        }

        baseVec[edge.source].emplace_back(edge.target);

        baseVec[edge.target].emplace_back(edge.source);

    }



    void display() {

        for (vector<vector<int>>::size_type i = 0; i < baseVec.size(); i++) {

            cout << "n Adjacency list of vertex " << i << "n head: ";

            for (vector<int>::size_type j = 0; j < baseVec[i].size(); j++)

                cout << baseVec[i][j] << " ";

            std::cout << std::endl;

        }

    }

};



int main() {

    int vertex;

    cout << "Enter number of nodes: ";

    cin >> vertex;



    Graph graph(vertex);



    while (true) {

        int source, target;

        cout << "Enter edge ex.1 2 (-1 -1 to exit): n";

        cin >> source >> target;

        if ((source == -1) && (target == -1))

            break;

        graph.newEdge({ source, target });

    }

    graph.display();

    return 0;

}

I really can't find many things to change, so I wrote the isConnected() function. Maybe it has some weaknesses or errors. Hope it's useful and I'm still waiting for advice. Thank you!

Code inside the class:

    bool isConected(std::vector<int> nodeVec)

        {



            for (st



d::vector<std::vector<int>>::size_type i = 0; i < baseVec.size(); i++)

        {

            if (baseVec[i].empty())

            {

                return false;

            }

        }

        for (std::vector<std::vector<int>>::size_type i = 0; i < baseVec.size(); i++)

        {

            for (std::vector<int>::size_type j = 0; j < baseVec[i].size() + 1; j++)

            {

                if (baseVec[i][j] == nodeVec[j + 1])

                {

                    return true;

                }

            }

        }

    }

The line in main:

std::vector<int> nodeVec;

    for (int i = 0; i < vertex; i++)

    {

        nodeVec.emplace_back(i);

    }

And:

if (graph.isConected(nodeVec) == true)

{

    std::cout << "Yesn";

}

else

{

    std::cout << "Non";

}

Some comments -

• 
  cout << "Invalid edge" is not a sane error-relaying mechanism. The C++ way to do things is to throw an exception. The calling code could catch the exception and print an error, or could let the app exit if this is a serious-enough error.


• 
  void display() needs to be void display() const. It doesn't modify anything.


• Don't iterate through an STL container using an integer index. Iterate using an iterator. If you don't know what I mean, google around or read https://www.geeksforgeeks.org/iterators-c-stl/