When you try to install 12c database, make sure you have correct content in /etc/oraInst.loc file.
I have the following content in the file /etc/oraInst.loc
[root@db12c 11.2.0]# cat oraInst.loc
inventory_loc=/home/apps/oraInventory/
[root@db12c 11.2.0]#
Cause: Installer has failed to detect the inventory group owner from the inventory pointer location file.
Then i modified the content as below which resolved the issue.
[root@db12c CentOS]# cat /etc/oraInst.loc
inventory_loc=/home/apps/oraInventory/
inst_group=dba
[root@db12c CentOS]#