Cod sursa(job #2737268)

Utilizator inwursuIanis-Vlad Ursu inwursu Data 4 aprilie 2021 16:37:43
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.7 kb
// BellmanFord.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <vector>
#include <fstream>
#include <tuple>
#include <queue>


using namespace std;

const int MAX_N = 50000 + 1;
const int MAX_M = 250000 + 1;
const int oo = static_cast<int>(1e9);


vector<vector<tuple<int, int>>> adj(MAX_N + 1, vector<tuple<int, int>>());
int N, M;
int s;

vector<int> d(MAX_N);
vector<int> cnt(MAX_N);


bool SPFA()
{
    for (int i = 1; i <= N; ++i)
    {
        d[i] = oo;
        cnt[i] = 0;
    }

    d[s] = 0;


    queue<int> Q;
    Q.push(s);
    cnt[s] = 1;

    while (Q.empty() == false)
    {
        int u = Q.front();
        Q.pop();

        for (auto& edge : adj[u])
        {
            int v = get<0>(edge);
            int weight = get<1>(edge);

            if (d[u] + weight < d[v])
            {
                d[v] = d[u] + weight;

                Q.push(v);
                cnt[v] += 1;

                if (cnt[v] == N)
                {
                    return false;
                }
            }
        }
    }


    return true;
}


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

    s = 1;


    fin >> N >> M;

    for (int i = 1; i <= M; ++i)
    {
        int u, v, weight;

        fin >> u >> v >> weight;

        adj[u].push_back({ v, weight });
    }


    bool ok = SPFA();

    if (ok == false)
    {
        fout << "Ciclu negativ!" << endl;
    }
    else
    {
        for (int i = 2; i <= N; ++i)
        {
            fout << d[i] << " ";
        }

        fout << endl;
    }

    return 0;
}