Cod sursa(job #1195198)

Utilizator juniorOvidiu Rosca junior Data 6 iunie 2014 17:36:47
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.52 kb
#include <fstream>
#include <vector>
#include <queue>
#include <bitset>
#include <algorithm>

using namespace std;

const int MAX_N = 50005;
const int INF = 0x3f3f3f3f;

vector < pair <int, int> > adj[MAX_N];

int main(void) {
  ifstream fi("bellmanford.in");
  int nodes, edges;
  fi >> nodes >> edges;
  for (int i = 0; i < edges; ++ i) {
    int x, y, c;
    fi >> x >> y >> c;
    adj[x].push_back(make_pair(y, c));
  }
  fi.close();

  queue <int> Q;
  bitset <MAX_N> in_queue(false);
  vector <int> dist(MAX_N, INF), cnt_in_queue(MAX_N, 0);
  int negative_cycle = false;

  dist[1] = 0, Q.push(1), in_queue[1] = true;
  while (!Q.empty() and !negative_cycle)  {
    int x = Q.front();
    Q.pop();
    in_queue[x] = false;
    vector < pair <int, int> >::iterator it;
    for (it = adj[x].begin(); it != adj[x].end(); it++)
      if (dist[x] < INF)
        if (dist[it->first] > dist[x] + it->second) { // distanta pana la it->first poate fi imbunatatita
          dist[it->first] = dist[x] + it->second;
          if (!in_queue[it->first])
            if (cnt_in_queue[it->first] > nodes)
              negative_cycle = true;
            else {
              Q.push(it->first);
              in_queue[it->first] = true;
              cnt_in_queue[it->first]++;
            }
        }
  }
  ofstream out("bellmanford.out");
  if (!negative_cycle) {
    for (int i = 2; i <= nodes; ++ i)
      out << dist[i] << " ";
  }
  else
    out << "Ciclu negativ!\n";
  out.close();
  return 0;
}