public static String encryption(String s) { int len = s.length(); int row = (int) Math.floor(Math.sqrt(len)); int col = (int) Math.ceil(Math.sqrt(len));

    if (row * col < len) {
        row++;
    }


    char[][] matrix = new char[row][col];


    int index = 0;
    for (int r = 0; r < row; r++) {
        for (int c = 0; c < col; c++) {
            if (index < len) {
                matrix[r][c] = s.charAt(index++);
            } else {
                matrix[r][c] = ' '; 
            }
        }
    }


    StringBuilder sb = new StringBuilder();
    for (int c = 0; c < col; c++) {
        if (c > 0) sb.append(" ");
        for (int r = 0; r < row; r++) {
            if (matrix[r][c] != ' ') {
                sb.append(matrix[r][c]);
            }
        }
    }

        return sb.toString();


}

• }