Cod sursa(job #3182326)

Utilizator manudragoDragomir Manuel manudrago Data 8 decembrie 2023 20:06:13
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.34 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;

ifstream fin("dijkstra.in");
ofstream fout("dijkstra.out");

const int NMAX = 50001;
const long long INF = 5000000000;

vector < pair < int, int > > G[NMAX];
long long dist[NMAX];
int N, M;

void read(){
    fin >> N >> M;
    for(int i = 0; i < M; i++){
        int x, y, c;
        fin >> x >> y >> c;
        G[x].push_back({y, c});
    }
}

void init(){
    for(int i = 1; i <= N; i++){
        dist[i] = INF;
    }
    dist[1] = 0;
}

bool relax(int x, int y, int c){
    if(dist[y] > dist[x] + c){
        dist[y] = dist[x] + c;
    }
}

queue < int > q;
int viz[NMAX];
void bellman_ford_optimizat(){
    q.push(1);
    while(!q.empty()){
        int nodc = q.front();
        q.pop();
        for(auto [nbr, cost]: G[nodc]){
            if(dist[nbr] > dist[nodc] + cost){
                dist[nbr] = dist[nodc] + cost;
                viz[nbr]++;
                q.push(nbr);
            }
        }
    }
}

/// are vreo diferenta daca punem (cost, nod) sau (nod, cost)?
priority_queue < pair < int, int > > pq;
void dijkstra_gresit(){
    pq.push({0, 1});
    while(!pq.empty()){
        auto [cost_nodc, nodc] = pq.top();
        pq.pop();
        viz[nodc] = 1;

        for(auto [nbr, cost]: G[nodc]){
            if(!viz[nbr] && dist[nbr] > dist[nodc] + cost){
                dist[nbr] = dist[nodc] + cost;
                pq.push({-dist[nbr], nbr});
            }
        }
    }
}

void dijkstra_corect(){
    pq.push({0, 1});
    while(!pq.empty()){
        auto [cost_nodc, nodc] = pq.top();
        pq.pop();

        /// ce rol are?
        if(viz[nodc]){
            continue;
        }

        viz[nodc] = 1;
        for(auto [nbr, cost]: G[nodc]){
            /// dist[nodc] != cost_nodc?
            if(!viz[nbr] && dist[nbr] > dist[nodc] + cost){
                dist[nbr] = dist[nodc] + cost;
                pq.push({-dist[nbr], nbr});
            }
        }
    }
}

int main()
{
    read();
    init();
    ///bellman_ford_optimizat();
    ///dijkstra_gresit();
    dijkstra_corect();
    for(int i = 2; i <= N; i++){
        if(dist[i] == INF){
            fout << 0 << " ";
        }else{
            fout << dist[i] << " ";
        }

    }
    return 0;
}