Best bet for table defragmentation

Its Oracle 9.2.0.7 on Solaris, we have a transaction table with approximately 68 million rows. It is consisting of about 100GB space in the tablespace and it is assumed that it is highly fragmented. We definitely need some space at that tablespace and for that we were discussing the methods for defragmenting it and get some space back. One suggested method was export/import but that would take atleast 6 hours while another one was moving the table to another tablespace and rebuild the indexes which would not require any downtime.  

Does any guru have any other suggestion regarding that? Or your input about the above methods as per knowledge and experience???  

Thanks,  

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