Dijkstras.cpp

#include <bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f


typedef pair<int, int> iPair;


class Graph
{
    int V; 
    
    list<pair<int, int>> *adj;

public:
    Graph(int V); 
    void addEdge(int u, int v, int w);

    // prints shortest path from s
    void shortestPath(int s);
};

// Allocates memory for adjacency list
Graph::Graph(int V)
{
    this->V = V;
    adj = new list<iPair>[V];
}

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

// Prints shortest paths from src to all other vertices
void Graph::shortestPath(int src)
{
    
    priority_queue<iPair, vector<iPair>, greater<iPair>>
        pq;

    // Create a vector for distances and initialize all
    // distances as infinite (INF)
    vector<int> dist(V, INF);

    // Insert source itself in priority queue and initialize
    // its distance as 0.
    pq.push(make_pair(0, src));
    dist[src] = 0;

    /* Looping till priority queue becomes empty (or all
    distances are not finalized) */
    while (!pq.empty())
    {
      
        int u = pq.top().second;
        pq.pop();

        
        list<pair<int, int>>::iterator i;
        for (i = adj[u].begin(); i != adj[u].end(); ++i)
        {
            
            int v = (*i).first;
            int weight = (*i).second;

           
            if (dist[v] > dist[u] + weight)
            {
                dist[v] = dist[u] + weight;
                pq.push(make_pair(dist[v], v));
            }
        }
    }

    
    printf("Vertex Distance from Source\n");
    for (int i = 0; i < V; ++i)
        printf("%d \t\t %d\n", i, dist[i]);
}


int main()
{
    int V = 7;
    Graph g(V);

    
    g.addEdge(0, 1, 2);
    g.addEdge(0, 2, 6);
    g.addEdge(1, 3, 5);
    g.addEdge(2, 3, 8);
    g.addEdge(3, 4, 10);
    g.addEdge(3, 5, 15);
    g.addEdge(4, 6, 2);
    g.addEdge(5, 6, 6);
    g.shortestPath(0);

    return 0;
}