C++ Graph Implementations

Can you explain how to implement a graph in C++?

Sure! In C++, you can implement a graph using an adjacency list or an adjacency matrix. Which one would you like to know more about?

I'd like to learn about the adjacency list.

Great choice! An adjacency list uses a vector of lists. Each index represents a vertex, and the list at that index contains the adjacent vertices.

Can you show me a simple code example?

Of course! Here's a basic implementation:

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

class Graph {
    int V; // Number of vertices
    vector<list<int>> adj;
public:
    Graph(int V);
    void addEdge(int v, int w);
    void printGraph();
};

Graph::Graph(int V) {
    this->V = V;
    adj.resize(V);
}

void Graph::addEdge(int v, int w) {
    adj[v].push_back(w);
}

void Graph::printGraph() {
    for (int v = 0; v < V; v++) {
        cout << "Vertex " << v << ":";
        for (int w : adj[v]) {
            cout << " " << w;
        }
        cout << endl;
    }
}

This code creates a graph and allows you to add edges.

How do I use this code to create a graph?

You can create a graph by instantiating the Graph class and using the addEdge method to add connections. For example:

int main() {
    Graph g(5); // Create a graph with 5 vertices
    g.addEdge(0, 1);
    g.addEdge(0, 4);
    g.addEdge(1, 2);
    g.addEdge(1, 3);
    g.addEdge(1, 4);
    g.addEdge(2, 3);
    g.addEdge(3, 4);
    g.printGraph();
    return 0;
}