3-Dijkstra.cpp

#include <iostream>
#include <queue>
#include <vector>
#include <climits>
using namespace std;
#define INF INT_MAX

const int sz = 10001;
vector<pair<int, int>> a[sz]; //Adjacency list
int dis[sz];                  //Stores shortest distance
bool vis[sz] = {0};

void Dijkstra(int source, int n)
{
    for (int i = 0; i < sz; i++)
        dis[i] = INF;
    class prioritize
    {
    public:
        bool operator()(pair<int, int> &p1, pair<int, int> &p2) { return p1.second > p2.second; }
    };
    priority_queue<pair<int, int>, vector<pair<int, int>>, prioritize> pq;
    pq.push(make_pair(source, dis[source] = 0));
    while (!pq.empty())
    {
        pair<int, int> curr = pq.top();
        pq.pop();
        int cv = curr.first, cw = curr.second;
        if (vis[cv])
            continue;
        vis[cv] = true;
        for (int i = 0; i < a[cv].size(); i++)
            if (!vis[a[cv][i].first] && a[cv][i].second + cw < dis[a[cv][i].first])
                pq.push(make_pair(a[cv][i].first, (dis[a[cv][i].first] = a[cv][i].second + cw)));
    }
}

int main()
{
    int n, m, x, y, w;
    cout << "Enter number of vertices and edges in the graph\n";
    cin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        cin >> x >> y >> w;
        a[x].push_back(make_pair(y, w));
        a[y].push_back(make_pair(x, w));
    }
    int source;
    cin >> source;
    Dijkstra(source, n);
    cout << "Source is: " << source << ". The shortest distance to every other vertex from here is: \n";
    for (int i = 1; i <= n; i++)
    {
        cout << "Vertex: " << i << " , Distance: ";
        dis[i] != INF ? cout << dis[i] << "\n" : cout << "-1\n";
    }
    return 0;
}

// 5
// 5 1
// 2 3
// 2 5
// 5 1
// 5 4
// 1 3
// 2 3
// 4 3
// 1