Cod sursa(job #1788030)

Utilizator andreiiiiPopa Andrei andreiiii Data 25 octombrie 2016 15:52:57
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.56 kb
#include <algorithm>
#include <fstream>
#include <cstring>
#include <cassert>
#include <vector>
#include <queue>
using namespace std;

const int NMAX = 50005;
const int INF = 0x3f3f3f3f;

vector<pair<int, int>> G[NMAX];

int dist[NMAX];

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

    int n, m;
    fin >> n >> m;
    assert(1 <= n && n <= 50000);
    assert(1 <= m && m <= 250000);

    for (int i = 0; i < m; ++i) {
        int from, to, cost;
        fin >> from >> to >> cost;
        assert(1 <= from && from <= n);
        assert(1 <= to && to <= n);
        assert(0 <= cost && cost <= 20000);
        G[from].push_back(make_pair(to, cost));
    }

    memset(dist, INF, sizeof dist);
    dist[1] = 0;
    priority_queue<pair<int, int>> q;
    q.push(make_pair(0, 1));
    while (!q.empty()) {
        int node = q.top().second;
        int d = -q.top().first;
        q.pop();

        if (d != dist[node]) {
            continue;
        }

        for (vector<pair<int, int>>::iterator it = G[node].begin(); it != G[node].end(); ++it) {
            int to = it->first;
            int cost = it->second;
            if (dist[to] > dist[node] + cost) {
                dist[to] = dist[node] + cost;
                q.push(make_pair(-dist[to], to)); // Se adauga distanta negativa pentru ca priority_queue e defapt un max heap
            }
        }
    }

    for (int i = 2; i <= n; ++i) {
        if (dist[i] == INF) {
            dist[i] = 0;
        }
        fout << dist[i] << ' ';
    }
    fout << '\n';

    fin.close();
    fout.close();
}