vector<string> bomberMan(int n, vector<string> grid) {
    auto new_grid = grid;
    int rows = grid.size();
    int cols = grid[0].size();
    
    // the same answers are cycling over, just need to pick the correct one
    if (n > 4) {
        n = n % 4 + 4;
    }
    
    // bomb identifier - switching between 'O' and 'x' to differentiate time of planting
    char b = 'x';
    
    for (int i=2; i<=n; i++) {
        if (i % 2 == 0) {
            // step 3 - filling empty fields with bombs
            for (int r=0; r<rows; r++) {
                for (int c=0; c<cols; c++) {
                    if (grid[r][c] == '.') {
                        grid[r][c] = b;
                    }
                }
            }
            
            // flipping bomb type
            if (b == 'x') b = 'O';
            else b = 'x';
        } else {
            // step 4 - exploding bombs planted at time i-3
            new_grid = grid;
            
            for (int r=0; r<rows; r++) {
                for (int c=0; c<cols; c++) {
                    if (grid[r][c] == b) {
                        if (r > 0) new_grid[r-1][c] = '.';
                        if (r < rows-1) new_grid[r+1][c] = '.';
                        if (c > 0) new_grid[r][c-1] = '.';
                        if (c < cols-1) new_grid[r][c+1] = '.';
                        new_grid[r][c] = '.';
                    }
                }
            }
            
            swap(new_grid, grid);
        }
    }
    
    // going back to default bomb labeling
    for (int r=0; r<rows; r++) {
        for (int c=0; c<cols; c++) {
            if (grid[r][c] == 'x') grid[r][c] = 'O';
        }
    }
    
    return grid;
}