Cod sursa(job #2654120)

Utilizator Florinos123Gaina Florin Florinos123 Data 29 septembrie 2020 20:40:37
Problema Algoritmul Bellman-Ford Scor 35
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.53 kb
#include <fstream>
#include <queue>
#include <vector>

using namespace std;

ifstream f ("bellmanford.in");
ofstream g ("bellmanford.out");

int n, m;

bool cycle;

int dist[50005];

int cnt[50005];

bool inq[50005];

const int INF = 100000000;

queue < int > q;

vector < pair < int, int > > v[250005];

void Read ()
{
    f >> n >> m;
    for (int i=1; i<=m; i++)
    {
        int x, y, cost;
        f >> x >> y >> cost;
        v[x].push_back(make_pair(y, cost));
    }

    for (int i=1; i<=n; i++)
        dist[i] = INF;
}

void BellmanFord (int start)
{
    inq[start] = 1, dist[start] = 0;
    q.push(start);

    while (!q.empty() && !cycle)
    {
        int nod = q.front();
        int lg = v[nod].size();
        q.pop();
        inq[nod] = 0;

        for (int i=0; i<lg; i++)
        {
            int nod_nou = v[nod][i].first;
            int cost = v[nod][i].second;

            if (dist[nod] + cost < dist[nod_nou])
            {
                dist[nod_nou] = dist[nod] + cost;

                cnt[nod_nou] = cnt[nod] + 1;
                if (cnt[nod_nou] > n-1) cycle = true;

                if (!inq[nod_nou])
                {
                    q.push(nod_nou);
                    inq[nod_nou] = 1;
                }
            }
        }
    }
}

void Print ()
{
    for (int i=2; i<=n; i++)
        g << dist[i] << " ";
}

int main()
{
    Read();
    BellmanFord(1);
    if (cycle) g << "Ciclu Negativ!";
    else Print();
    return 0;
}