What is a graph data structure in C++?

What is a graph data structure in C++?

A graph data structure consists of nodes (vertices) and edges connecting them. In C++, it can be implemented using adjacency lists or matrices.

Can you show me an example of how to implement a graph using an adjacency list?

Sure! Here's a simple implementation:

#include <iostream>
#include <vector>
#include <list>

class Graph {
    int V; // Number of vertices
    std::vector<std::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++) {
        std::cout << "Vertex " << v << " : ";
        for (int w : adj[v]) {
            std::cout << w << " ";
        }
        std::cout << std::endl;
    }
}

int main() {
    Graph g(5);
    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;
}

What are the advantages of using an adjacency list over an adjacency matrix?

Adjacency lists are more space-efficient for sparse graphs, as they only store edges that exist. They also allow for faster iteration over neighbors compared to adjacency matrices.