Cod sursa(job #2978545)

Utilizator SabailaCalinSabaila Calin SabailaCalin Data 13 februarie 2023 21:25:03
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.78 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;

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

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

struct Compare
{
    inline bool operator() (pair <int, int> x, pair <int, int> y)
    {
        return x.second > y.second;
    }
};

int n, m;

vector < pair <int, int> > adj[SIZE];
vector <int> dist(SIZE, INF);

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

bool BellmanFord(int startNode)
{
    priority_queue < pair <int, int>, vector < pair <int, int> >, Compare> pq;
    vector <int> cntInQueue(SIZE, 0);

    dist[startNode] = 0;
    pq.push(make_pair(startNode, dist[startNode]));

    while (pq.empty() == false)
    {
        int node = pq.top().first;
        int distanceToNode = pq.top().second;
        cntInQueue[node]++;
        pq.pop();

        if (cntInQueue[node] >= n - 1)  return false;
        if (dist[node] < distanceToNode)  continue;

        for (unsigned int i = 0; i < adj[node].size(); i++)
        {
            int neighbour = adj[node][i].first;
            int cost = adj[node][i].second;

            if (distanceToNode + cost < dist[neighbour])
            {
                dist[neighbour] = distanceToNode + cost;
                pq.push(make_pair(neighbour, dist[neighbour]));
            }
        }
    }

    return true;
}

int main()
{
    Read();
    if (BellmanFord(1) == false)
    {
        g << "Ciclu negativ!";
    }
    else
    {
        for (int i = 2; i <= n; i++)
        {
            g << dist[i] << " ";
        }
    }

    return 0;
}