Cod sursa(job #2691805)

Utilizator andrei_laurentiuRadu Andrei-Laurentiu andrei_laurentiu Data 30 decembrie 2020 02:42:12
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 4.03 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <bitset>
#include <algorithm>
#include <cassert>
using namespace std;

const char iname[] = "bellmanford.in";
const char oname[] = "bellmanford.out";

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

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

int main(void) {
    ifstream in(iname);
    int nodes, edges;
    assert(in >> nodes >> edges);
    assert(1 <= nodes && nodes <= 50000);
    assert(1 <= edges && edges <= 250000);
    for (int i = 0; i < edges; ++ i) {
        int x, y, c;
        assert(in >> x >> y >> c);
        assert(1 <= x && x <= nodes);
        assert(1 <= y && y <= nodes);
        assert(-1000 <= c && c <= 1000);
        adj[x].push_back(make_pair(y, c));
        assert(find(adj_t[x].begin(), adj_t[x].end(), y) == adj_t[x].end());
        adj_t[x].push_back(y);
    }
    in.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].flip();
    while (!Q.empty() && !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) {
                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(oname);
    if (!negative_cycle) {
        for (int i = 2; i <= nodes; ++ i)
            out << dist[i] << " ";
    }
    else
        out << "Ciclu negativ!\n";
    out.close();

    return 0;
}
/*#include <iostream>
#include <vector>
#include <fstream>
#include <queue>
#include <bitset>

using namespace std;

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

int n, m, ok;
const int nmax = 50005, val_mare =  0x3f3f3f3f;
int negative_cycle;
vector<pair<int, int> > list_vec[nmax];
int dist[nmax];

void bellman_ford_q(int start)
{
    queue <int> q;
    bitset <nmax> in_coada(false);
    int contor_in_coada[nmax], i;
    //vector <int> dist(MAX_N, INF), in_coada(MAX_N, 0);

    for(i = 1; i <= n; ++i)
        dist[i] = val_mare;

    dist[start] = 0;
    q.push(start);
    in_coada[start] = 1;

    int curent, vecin, cost;

    while (!q.empty() && !negative_cycle)
    {
        curent = q.front();
        q.pop();
        in_coada[curent] = false;

        for(auto it : list_vec[curent])
        {
            if(dist[curent] < val_mare)
            {
                vecin = it.first;
                cost = it.second;
                if (dist[vecin] > dist[curent] + cost)
                {
                    dist[vecin] = dist[curent] + cost;
                    if (!in_coada[vecin])
                    {
                        if (contor_in_coada[vecin] > n)
                            negative_cycle = true;
                        else
                        {
                            q.push(vecin);
                            in_coada[vecin] = true;
                            contor_in_coada[vecin]++;
                        }
                    }
                }
            }
        }
    }
}
int main()
{
    int u, v, c, i;
    fin>>n>>m;

    for(i = 1; i <= m; ++i)
    {
        fin>>u>>v>>c;
        list_vec[u].push_back({v, c});
    }

    bellman_ford_q(1);

    if(negative_cycle)
        fout<<"Ciclu negativ!";
    else
    {
        for(i = 2; i <= n; ++i)
            fout<<dist[i]<<' ';
    }
    return 0;
}*/