C++ Dijkstra Algorithm using the priority queue

#include <iostream>
#include <vector>
#include <queue>
#include <climits>

using namespace std;

// Define an edge structure to represent edges in the graph
struct Edge {
    int to;
    int weight;
    Edge(int _to, int _weight) : to(_to), weight(_weight) {}
};

// Define a custom comparison function for the priority queue
struct Compare {
    bool operator()(const pair<int, int>& a, const pair<int, int>& b) const {
        return a.second > b.second;
    }
};

// Function to perform Dijkstra's algorithm
void dijkstra(const vector<vector<Edge>>& graph, int source) {
    int n = graph.size();
    vector<int> distance(n, INT_MAX);
    vector<bool> visited(n, false);

    priority_queue<pair<int, int>, vector<pair<int, int>>, Compare> pq;

    distance[source] = 0;
    pq.push({source, 0});

    while (!pq.empty()) {
        int u = pq.top().first;
        pq.pop();

        if (visited[u]) continue;
        visited[u] = true;

        for (const Edge& edge : graph[u]) {
            int v = edge.to;
            int w = edge.weight;

            if (!visited[v] && distance[u] + w < distance[v]) {
                distance[v] = distance[u] + w;
                pq.push({v, distance[v]});
            }
        }
    }

    // Print the shortest distances from the source vertex
    cout << "Shortest distances from vertex " << source << ":\n";
    for (int i = 0; i < n; ++i) {
        cout << "Vertex " << i << ": " << distance[i] << endl;
    }
}

int main() {
    int n = 6; // Number of vertices
    vector<vector<Edge>> graph(n);

    // Adding edges to the graph
    graph[0].push_back(Edge(1, 2));
    graph[0].push_back(Edge(2, 4));
    graph[1].push_back(Edge(2, 1));
    graph[1].push_back(Edge(3, 7));
    graph[2].push_back(Edge(4, 3));
    graph[3].push_back(Edge(4, 1));
    graph[3].push_back(Edge(5, 5));
    graph[4].push_back(Edge(5, 2));

    int source = 0; // Source vertex

    dijkstra(graph, source);

    return 0;
}