Cod sursa(job #3262891)

Utilizator DragosVNVisanescu Dragos Nicholas DragosVN Data 11 decembrie 2024 21:40:19
Problema Algoritmul lui Dijkstra Scor 90
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.68 kb
#include <iostream>
#include <fstream>
#include <queue>
#include <vector>
using namespace std;

ifstream f("dijkstra.in");
ofstream g("dijkstra.out");

const int inf=100000;
typedef pair<int, int> iPair;   //definim un pair de int-uri pt simplificarea sintaxei
vector < vector < iPair > > G(50005); // first - nodul , second - costul

int n,m;
void citire()
{
    f>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y,c;
        f>>x>>y>>c;
        G[x].push_back(make_pair(c,y));

    }
}
void Dijkstra(int start)
{
    //ATENTIE - la priority queue distanta trebuie sa fie PRIMA in pair. Altfel nodurile vor iesi in ordinea etichetelor lor,
    //nu a distantei pana la start.
    priority_queue < iPair , vector < iPair >, greater<iPair> > pq; //declaram min-heap ul
    vector <int> d(50005,inf);  //vectorul de distante

    d[start]=0;
    pq.push(make_pair(0,start));


    while(!pq.empty())
    {
        int nodmin=pq.top().second; //luam nodul cel mai apropait de start din coada de prioritati
        pq.pop();

        for(int i=0;i<G[nodmin].size();i++) //ii parcurgem vecinii nodului
        {
            int v = G[nodmin][i].second;    //luam vecinul nodului minim
            int weight = G[nodmin][i].first;    //luam distanta de la nodul minim la vecin
            int dn=d[nodmin]+weight;
            if(d[v]>dn)   //relaxam daca e cazul
            {
                d[v]=dn;
                pq.push(make_pair(d[v],v));
            }
        }
    }

    for(int i=2;i<=n;i++)
    {
        if(d[i]==inf)
        g<<0<<" ";
    else
        g<<d[i]<<" ";
    }
}
int main()
{
    citire();
    Dijkstra(1);

    return 0;
}