Cod sursa(job #2683564)

Utilizator Silviu.Stancioiu@gmail.comSilviu Stancioiu [email protected] Data 11 decembrie 2020 16:54:27
Problema Algoritmul Bellman-Ford Scor 20
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.71 kb
#include <fstream>
#include <queue>
#include <vector>

constexpr auto max_n = 50005;

using namespace std;

ifstream fin("bellmanford.in");
ofstream fout("bellmanford.out");
int n, m;
vector<pair<int, int>> graph[max_n];
bool is_in_queue[max_n];
int min_dist[max_n];
int cycle_times[max_n];

int main()
{
    fin >> n >> m;

    for (auto i = 0; i < m; i++)
    {
        int a, b, c;
        fin >> a >> b >> c;
        graph[a].push_back(make_pair(b, c));
    }

    for (auto i = 1; i <= n; i++)
        min_dist[i] = 0x3f3f3f3f;

    queue<int> nodes_queue;
    nodes_queue.push(1);
    min_dist[1] = 0;
    is_in_queue[1] = true;
    bool negative_cycle = false;

    while (!nodes_queue.empty() && !negative_cycle)
    {
        const auto crt_node = nodes_queue.front();
        nodes_queue.pop();

        is_in_queue[crt_node] = false;

        for (auto &neigh : graph[crt_node])
        {
            if (!is_in_queue[neigh.first])
            {
                if (min_dist[neigh.first] > min_dist[crt_node] + neigh.second)
                {
                    if (cycle_times[neigh.first] > n)
                        negative_cycle = true;
                    else
                    {
                        min_dist[neigh.first] = min_dist[crt_node] + neigh.second;
                        cycle_times[neigh.first]++;
                        is_in_queue[neigh.first] = true;
                        nodes_queue.push(neigh.first);
                    }
                }
            }
        }
    }

    if (negative_cycle)
        fout << "Ciclu negativ!";
    else
        for (auto i = 2; i <= n; i++)
            fout << min_dist[i] << " ";

    return 0;
}