Cod sursa(job #2860678)

Utilizator pandurelPanduru Andrei pandurel Data 2 martie 2022 22:12:55
Problema Algoritmul Bellman-Ford Scor 15
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.83 kb
#include <iostream>
#include <fstream>
#include <queue>
#include <vector>

#define NMax 50005
#define oo (1 << 30)

using namespace std;

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

int N, D[NMax];
bool inCoada[NMax];

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

struct Compara
{
    bool operator() (int x, int y)
    {
        return D[x] > D[y];
    }
};
priority_queue < int, vector<int>, Compara > Coada;

void Citire()
{
    int A, B, C, M;

    fin >> N >> M;

    for(int i=1; i<=M; ++i)
    {
        fin >> A >> B >> C;
        G[A].push_back( make_pair(B, C) );
    }
}

void BellmanFord(int nodStart)
{
    for(int i=1; i<=N; ++i)
        D[i] = oo;

    D[nodStart] = 0;
    Coada.push(nodStart);
    inCoada[nodStart] = true;

    while( !Coada.empty() )
    {
        int nodCurent = Coada.top();
        Coada.pop();
        inCoada[nodCurent] = false;

        for(unsigned int i = 0; i < G[nodCurent].size(); ++i)
        {
            int Vecin = G[nodCurent][i].first;
            int Cost = G[nodCurent][i].second;

            if(D[nodCurent] + Cost < D[Vecin])
            {
                D[Vecin] = D[nodCurent] + Cost;

                if(inCoada[Vecin] == false)
                {
                    Coada.push(Vecin);
                    inCoada[Vecin] = true;
                }
            }
        }
    }
}

int main()
{
    Citire();

    int ok = 1;
    for(int i = 1; i <= N; ++ i)
    {
        BellmanFord(i);
        if(D[i] < 0)
        {
            ok = 0;
            fout << "Ciclu negativ!";
            break;
        }
    }

    if(ok)
    {
        BellmanFord(1);
        for(int i = 1; i <= N; ++ i)
            if(D[i] != oo  &&  D[i] != 0)
                fout << D[i] << ' ';
    }

    return 0;
}