Cod sursa(job #790670)

Utilizator a_h1926Heidelbacher Andrei a_h1926 Data 22 septembrie 2012 00:26:36
Problema BFS - Parcurgere in latime Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.02 kb
#include <cstdio>
#include <vector>
#include <queue>

using namespace std;

const int MaxN = 100005;
const int oo = 1000000;

vector<int> G[MaxN];
int N, Start, D[MaxN];
queue<int> Q;

void InitBFS(int S) {
    for (int X = 1; X <= N; ++X)
        D[X] = oo;
    D[S] = 0, Q.push(S);
}

void BFS(int S) {
    for (InitBFS(S); !Q.empty(); Q.pop()) {
        int X = Q.front();
        for (vector<int>::iterator Y = G[X].begin(); Y != G[X].end(); ++Y)
            if (D[X]+1 < D[*Y])
                D[*Y] = D[X]+1, Q.push(*Y);
    }
}

void Read() {
    freopen("bfs.in", "r", stdin);
    int M; scanf("%d %d %d", &N, &M, &Start);
    for (; M; --M) {
        int X, Y; scanf("%d %d", &X, &Y);
        G[X].push_back(Y);
    }
}

void Print() {
    freopen("bfs.out", "w", stdout);
    for (int X = 1; X <= N; ++X) {
        if (D[X] == oo)
            D[X] = -1;
        printf("%d ", D[X]);
    }
    printf("\n");
}

int main() {
    Read();
    BFS(Start);
    Print();
    return 0;
}