TheAlgorithms-C-Plus-Plus/Graph/Dijkstra.cpp

#include <queue>
#include <vector>
#include <cstdio>
#include <iostream>
using namespace std;
#define INF 10000010
vector < pair <int,int> > graph[5*100001];
int dis[5*100001];
int dij(vector <pair<int,int> > * v,int s,int * dis) {
    priority_queue < pair <int,int> , vector < pair <int,int> >,greater < pair <int,int> > > pq;
    // source distance to zero.
    pq.push(make_pair(0,s));
    dis[s] = 0;
    int u;
    while(!pq.empty()) {
        u = (pq.top()).second;
        pq.pop();
        for( vector <pair <int,int> > :: iterator it = v[u].begin(); it != v[u].end();it++) {
            if(dis[u] + it->first < dis[it->second]) {
                dis[it->second] = dis[u] + it->first;
                pq.push(make_pair(dis[it->second],it->second));
            }
        }
    }
}
int main() {
    int m,n,l,x,y,s;
    // n--> number of nodes , m --> number of edges
    cin>>n>>m;
    for(int i = 0;i < m;i++) {
        // input edges.
        scanf("%d%d%d",&x,&y,&l);
        graph[x].push_back(make_pair(l,y));
        graph[y].push_back(make_pair(l,x)); // comment this line for directed graph
    }
    // start node.
    scanf("%d",&s);
    // intialise all distances to infinity.
    for(int i = 1;i <= n;i++)
        dis[i] = INF;
    dij(graph,s,dis);
    
    for(int i = 1;i <= n;i++)
        if(dis[i] == INF)
            cout<<"-1 ";
        else
            cout<<dis[i]<<" ";
    return 0;
}