Graph implementation in C++ using adjacency list

Question

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 << "Yes\n";
}
else
{
 std::cout << "No\n";
}

Answer 1

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/

• Top4o: What do you mean to "Don't iterate through an STL container using an integer index."? Which lines I have to change?
• Reinderien: for (vector<vector<int>>::size_type i = 0; i < baseVec.size(); i++) {