Cod sursa(job #2791003)

Utilizator witekIani Ispas witek Data 29 octombrie 2021 22:31:20
Problema BFS - Parcurgere in latime Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.1 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

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

vector <vector <int>> v;
vector <int> d;
vector <bool> visited;
queue <int> q;
int n, m, s;
const int oo = 2e9;

void init() {
    v = vector <vector <int>> (n + 1);
    visited = vector <bool> (n + 1);
    d = vector <int> (n + 1, oo);
}

void read() {
    f >> n >> m >> s;
    init();
    int x, y;
    for(int i = 1; i <= m; ++i) {
        f >> x >> y;
        v[x].push_back(y);
    }

}

void bfs() {
    q.push(s);
    visited[s] = true;
    d[s] = 0;
    int node;
    while(!q.empty()) {
        node = q.front();
        q.pop();
        for(const int& neighbour : v[node]) {
            if(!visited[neighbour] && (d[node] + 1 < d[neighbour])) {
                q.push(neighbour);
                visited[neighbour] = true;
                d[neighbour] = d[node] + 1;
            }
        }
    }
}

int main()
{
    read();
    bfs();
    for(int i = 1; i <= n; ++i)
        g << (d[i] != oo ? d[i] : -1) << " ";
}