Cod sursa(job #1483585)

Utilizator AdrianaMAdriana Moisil AdrianaM Data 9 septembrie 2015 16:37:53
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.43 kb
#include <fstream>
#include <vector>
#include <queue>
#include <bitset>
#define INF 0x3f3f3f3f
using namespace std;

ifstream is("bellmanford.in");
ofstream os("bellmanford.out");

using VI = vector<int>;
using VII = vector<pair<int, int>>;
using VVII = vector<VII>;

int n, m;
VI d;
VVII g;

bool BF();

int main()
{
    is >> n >> m;
    g = VVII(n + 1);
    int a, b, c;
    for ( int i = 1; i <= m; ++i )
    {
        is >> a >> b >> c;
        g[a].push_back(make_pair(c, b));
    }
    if ( !BF() )
        os << "Ciclu negativ!";
    else
        for ( int i = 2; i <= n; ++i )
            os << d[i] << " ";
    is.close();
    os.close();
    return 0;
}

bool BF()
{
    d = VI(n + 1, INF);
    d[1] = 0;
    VI cnt(n + 1);
    bitset<50001> ok;
    queue<int> q;
    q.push(1);
    int nod;
    while ( !q.empty() )
    {
        nod = q.front();
        q.pop();
        ok[nod] = false;
        for ( const auto& nodv : g[nod] )
            if ( d[nodv.second] > d[nod] + nodv.first )
            {
                d[nodv.second] = d[nod] + nodv.first;
                if ( !ok[nodv.second] )
                {
                    ++cnt[nodv.second];
                    if ( cnt[nodv.second] == n )
                        return false;
                    ok[nodv.second] = true;
                    q.push(nodv.second);
                }
            }
    }
    return true;
}