P21600: El joc de la vida (1)

#include <iostream>
#include <vector>
using namespace std;


typedef vector<char> Row;
typedef vector<Row> Matrix;

void read_matrix(Matrix& M) {
    int f = M.size();
    int c = M[0].size();
    for (int i = 0; i < f; ++i) {
        for (int j = 0; j < c; ++j) {
            cin >> M[i][j];
        }
    }
}

void wrote_matrix(Matrix& M) {
    int f = M.size();
    int c = M[0].size();
    for (int i = 0; i < f; ++i) {
        for (int j = 0; j < c; ++j) {
            cout << M[i][j];
        }
        cout << endl;
    }
}

int count_pos(const Matrix& M, int i, int j) {
    int f = M.size();
    int c = M[0].size();
    int add_i = i + 1;
    int add_j = j + 1;
    int sub_i = i - 1;
    int sub_j = j - 1;
    bool exists_add_i = add_i < f;
    bool exists_add_j = add_j < c;
    bool exists_sub_i = sub_i >= 0;
    bool exists_sub_j = sub_j >= 0;
    int count = 0;
    if (exists_sub_i && M[sub_i][j] == 'B') ++count; //Nord
    if (exists_sub_j && M[i][sub_j] == 'B') ++count; //Oest
    if (exists_add_i && M[add_i][j] == 'B') ++count; //Sud
    if (exists_add_j && M[i][add_j] == 'B') ++count; //Est
    if (exists_sub_i && exists_sub_j && M[sub_i][sub_j] == 'B') ++count; //Nord-oest
    if (exists_sub_i && exists_add_j && M[sub_i][add_j] == 'B') ++count; //Nord-est
    if (exists_add_i && exists_add_j && M[add_i][add_j] == 'B') ++count; //Sud-est
    if (exists_add_i && exists_sub_j && M[add_i][sub_j] == 'B') ++count; //Sud-oest
    return count;
}

Matrix modify_matrix(const Matrix& M) {
    int f = M.size();
    int c = M[0].size();
    Matrix next_state(f, Row(c));
    next_state = M;
    for (int i = 0; i < f; ++i) {
        for (int j = 0; j < c; ++j) {
            int aux = count_pos(M, i, j);
            if (M[i][j] == '.' && aux == 3) next_state[i][j] = 'B';
            else if (M[i][j] == 'B' && aux != 2 && aux != 3) next_state[i][j] = '.';
        }
    }
    return next_state;
}

int main() {
    int f, c;
    bool primer = true;
    while (cin >> f >> c && (f != 0 && c != 0)) {
        if (not primer) cout << endl;
        else primer = false;
        Matrix M(f, Row(c));
        read_matrix(M);
        Matrix Result(f, Row(c));
        Result = modify_matrix(M);
        wrote_matrix(Result);
    }
}