how to get last logon user details of a particular computer from active directory. Note computer is not online, we have to get it from the ad logs , how? please 

You could check the logon information in event log. u can enable auditing for account logon events. These events (including workstation unlock) will be stored in the DC's security log.

https://technet.microsoft.com/en-us/library/cc787567%28WS.10%29.aspx?f=255&MSPPError=-2147217396

 you can record log on activity through group policy as well.. follow below page..

http://social.technet.microsoft.com/wiki/contents/articles/20422.record-logon-logoff-activities-on-domain-servers-and-workstations-using-group-policy.aspx

Here is a similar thread discussed before. Maybe you could refer to.

https://social.technet.microsoft.com/Forums/en-US/859384b1-6ec0-449c-bb2e-ad1f22e8e912/get-last-logon-timecomputer-and-username-together-with-powershell?forum=winserverpowershell

http://stackoverflow.com/questions/19983085/using-powershell-to-gather-logged-on-user-names-on-remote-computers

Best Regards,
Jitendra