Cod sursa(job #1128341)

Utilizator 2dorTudor Ciurca 2dor Data 27 februarie 2014 16:37:46
Problema BFS - Parcurgere in latime Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.07 kb
#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

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

const int MAXN = 100005;
const int INF = 0x3f3f3f3f;

int N, M, S;
int cost[MAXN];
queue<int> Q;
vector<int> G[MAXN];

void Read() {
    fin >> N >> M >> S;
    int a, b;
    for (int i = 0; i < M; ++i) {
        fin >> a >> b;
        G[a].push_back(b);
    }
}

void BFS(int S) {
    Q.push(S);
    cost[S] = 0;
    do {
        int node = Q.front();
        Q.pop();
        vector<int>::iterator it;
        for (it = G[node].begin(); it != G[node].end(); ++it) {
            if (cost[*it] > cost[node] + 1) {
                cost[*it] = cost[node] + 1;
                Q.push(*it);
            }
        }
    }while (!Q.empty());
}

void Write() {
    for (int i = 1; i <= N; ++i) {
        fout << (cost[i] == INF ? -1 : cost[i]) << ' ';
    }
}

int main() {
    Read();
    memset(cost, INF, sizeof(cost));
    BFS(S);
    Write();
    fin.close();
    fout.close();
    return 0;
}