07. Fill the Matrix

#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main() {
    string line;
    getline(cin, line);

    int n = stoi(line.substr(0, line.find(',')));
    string method = line.substr(line.size() - 1);

    vector<vector<int>> matrix;

    for (size_t i = 0; i < n; i++) {
        matrix.push_back(vector<int>(n));
    }

    int counter = 1;

    for (int c = 0; c < n; c++) {
        if (c % 2 == 1 && method == "B") {
            for (int r = n - 1; r >= 0; r--) {
                matrix[r][c] = counter++;
            }
        }
        else {
            for (int r = 0; r < n; r++) {
                matrix[r][c] = counter++;
            }
        }
    }


    for (int r = 0; r < n; r++) {
        for (int c = 0; c < n; c++) {
            cout << matrix[r][c] << ' ';
        }
        cout << endl;
    }

    return 0;
}