Print matrix paths

matrixpaths.java

// java.util.* and java.util.streams.* have been imported for this problem.
// You don't need any other imports.

public ArrayList<String> printPaths(char[][] board){
    StringBuilder sb = new StringBuilder();

    ArrayList<String> paths = new ArrayList<String>();
    
    if(board.length ==0 || board[0].length==0) return paths;
    
    helper(board, sb, 0, 0, paths);
    System.out.println(sb.toString());
    return paths;
}


private void helper(char[][] board, StringBuilder sb, int x, int y, ArrayList<String> paths) {
    
    int rows = board.length;
    int cols = board[0].length;
    
    
     sb.append(board[x][y]);
     
    if(x==rows-1 && y==cols-1) {
        paths.add(sb.toString());
        sb.deleteCharAt(sb.length()-1); // Un-Mark
        return;
    }
    
    if (x<rows-1)
        helper(board, sb, x+1, y, paths);
    if (y<cols-1)
        helper(board, sb, x, y+1, paths);
        
     sb.deleteCharAt(sb.length()-1); // Un-Mark
    
}