Cod sursa(job #3348210)

Utilizator radeuojArghira Radu Stefan radeuoj Data 20 martie 2026 11:03:09
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.57 kb
#include <iostream>
#include <queue>
#include <vector>

const int MAX_N = 50000;
const int MAX_M = 250000;
const int INF = 1e9;

struct Edge {
    int v, c;
};

struct Node {
    std::vector<Edge> adj;
    bool enqueued;
    int relax_count;
    int d;
};

int n, m;
Node a[MAX_N + 1];
std::queue<int> q;

void read_graph() {
    for (int i = 0; i < m; i++) {
        int u, v, c;
        std::cin >> u >> v >> c;
        a[u].adj.push_back({ v, c });
    }
}

// returns true if there is a negative cycle
bool spfa() {
    a[1].d = 0;
    q.push(1);
    a[1].enqueued = true;

    while (!q.empty()) {
        int u = q.front();
        q.pop();
        a[u].enqueued = false;

        for (auto [v, c] : a[u].adj) {
            if (a[u].d + c < a[v].d) {
                a[v].d = a[u].d + c;

                if (!a[v].enqueued) {
                    q.push(v);
                    a[v].enqueued = true;
                    a[v].relax_count++;

                    if (a[v].relax_count > n) {
                        return true; // negative cycle
                    }
                }
            }
        }
    }

    return false;
}

void print_distances() {
    for (int i = 2; i <= n; i++) {
        std::cout << a[i].d << ' ';
    }
}

void reset_distances() {
    for (int i = 1; i <= n; i++) {
        a[i].d = INF;
    }
}

int main() {
    freopen("bellmanford.in", "r", stdin);
    freopen("bellmanford.out", "w", stdout);

    std::cin >> n >> m;
    read_graph();
    reset_distances();

    if (spfa()) {
        std::cout << "Ciclu negativ!";
    } else {
        print_distances();
    }
}