Cod sursa(job #2365210)

Utilizator BurlacuMateiBurlacu Matei BurlacuMatei Data 4 martie 2019 12:34:19
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.58 kb
#include <fstream>
#include <queue>
#include <vector>
#define MAX 50002
#define INF 500000000

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

int n, start = 1;
int cmin[MAX]; //cmin[x] costul drumului de cost minim de la start la x
int nr[MAX]; // nr[x] este de cate ori a fost actualizat costul drumului de cost minim de la n la x
struct varf{int x, c;};
vector <varf> G[MAX];
queue <int> C;

void citire();
bool bellman_ford();

int main()
{int i;

    citire();
    if(!bellman_ford())
        fout <<"Ciclu negativ!";
    else for(i=2;i<=n;i++)
        if(cmin[i] == INF) fout << -1 << ' ';
        else fout << cmin[i] << ' ';

    fout.close();

    return 0;
}

void citire()
{
 int i, j, k, m, c;
 varf aux;

 fin>>n>>m;
 for(k=0;k<m;k++)
     {

        fin >> i >> j >> c;
        aux.x = j;
        aux.c = c;
        G[i].push_back(aux);

     }
}

bool bellman_ford()
///return 0 daca nu e solutie
///else return 1
{int vf, i;

    ///initializare
    for(i=1;i<=n;i++) cmin[i] = INF;
    cmin[start] = 0;


    C.push(start);
    while(!C.empty())
    {
        vf = C.front();
        C.pop();
        ///parcurg lista de adiacenta a lui x
        for(i=0;i<G[vf].size();i++)
        {
            if(cmin[G[vf][i].x] > cmin[vf] + G[vf][i].c)
            {
                cmin[G[vf][i].x] = cmin[vf] + G[vf][i].c;
                nr[G[vf][i].x]++;
                if(nr[G[vf][i].x] == n) return 0;
                C.push(G[vf][i].x);
            }
        }
    }

    return 1;
}