Cod sursa(job #2019328)

Utilizator bcrisBianca Cristina bcris Data 7 septembrie 2017 15:14:14
Problema Algoritmul lui Dijkstra Scor 10
Compilator cpp Status done
Runda Arhiva educationala Marime 1.9 kb
#include <stdio.h>
#include <vector>
#include <limits>
 
using namespace std;
 
#define NMAX 50005
#define INF 1 << 30 
 
int n, m;
int visited[NMAX], distances[NMAX], parent[NMAX];
vector<pair<int, int> > lista[NMAX];
 
using namespace std;
 
 
void read() {
    scanf("%d %d\n", &n, &m);
    int a, b, c;
    for (int i = 0 ; i < m; i++) {
        scanf("%d %d %d\n", &a, &b, &c);
        lista[a].push_back(std::make_pair(b, c));
    }
}
 
void dijkstra(int begin_node) {
    visited[begin_node] = 1;
    for (int i = 1; i <= n; i++) {
        distances[i] = INF;
        parent[i] = begin_node;
    } 
 
    for (vector<pair<int, int> >::iterator it = lista[begin_node].begin(); it != lista[begin_node].end(); ++it) {
        distances[(*it).first] = (*it).second;
    }
 
    int nodes_visited = 1;
 
    while (nodes_visited < n) {
        int min_distance = INF;
        int next_node = -1;
        for (int i = 1; i <= n; i++) {
            if (visited[i] == 0 && distances[i] < min_distance) {
                min_distance = distances[i];
                next_node = i;
            }
        }
 
        if (next_node == -1)
            return;
        visited[next_node] = 1;
        nodes_visited++;
         
        for (vector<pair<int, int> >::iterator it = lista[next_node].begin(); it != lista[next_node].end(); ++it) {
            int neighbour = (*it).first;
            int cost = (*it).second;
            if (!visited[neighbour]) {
                if (distances[next_node] + cost < distances[neighbour]) {
                    distances[neighbour] = distances[next_node] + cost;
                    parent[neighbour] = next_node;
                }
            }
        }   
    }       
}
 
int main() {
 
    freopen("dijkstra.in", "r", stdin);
    freopen("dijkstra.out", "w", stdout);
     
 
    read();
 
    dijkstra(1);
 
    for (int i = 2; i <= n; i++) {
        printf("%d ", distances[i]);
    }
    return 0;
}