Cod sursa(job #1920048)

Utilizator mariapascuMaria Pascu mariapascu Data 9 martie 2017 22:14:21
Problema BFS - Parcurgere in latime Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1 kb
#include <fstream>
#include <queue>
#include <vector>
using namespace std;

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

const int INF = 0x3f3f3f3f;
int n, m, S;
vector<vector<int>> G;
vector<int> D;
queue<int> Q;

void Read();
void BFS();
void Write();

int main() {
    Read();
    BFS();
    Write();

    fin.close();
    fout.close();
    return 0;
}

void BFS() {
    D[S] = 0;
    Q.push(S);
    int x;
    while (!Q.empty()) {
        x = Q.front(); Q.pop();
        for (const auto & y : G[x])
            if (D[y] == INF) {
                D[y] = D[x] + 1;
                Q.push(y);
            }
    }
}

void Write() {
    for (int i = 1; i <= n; i++)
        if (D[i] == INF) fout << "-1 ";
        else fout << D[i] << ' ';
}

void Read() {
    fin >> n >> m >> S;
    G = vector<vector<int>>(n + 1);
    D = vector<int>(n + 1, INF);
    int x, y;
    for (int i = 1; i <= m; i++) {
        fin >> x >> y;
        G[x].push_back(y);
    }
}