I recently read about how disk digger app works for android, I wanted to know if the app could search the memory and find the deleted files even after doing factory reset?
While I see that Disk Digger does advertise that it can recover files from formatted drives, I sort of doubt that it can do anything to recover files lost in a factory reset, insofar as the reset involves deleting the contents of the drive and replacing them with something new. (And usually, the factory reset covers all of the partitions of your SD card / internal memory, including your "Data" partition, where user files are stored.)
That said, if the deleted files were associated with a Google app, or with a game that had Google Play Services enabled (and your Google account connected), they might be restored when you re-associate the factory-reset device with your Google account.
Sorry I couldn't be more helpful...
Yes, it should be able to recover files after a reset. That is, any deleted files from before the reset are still deleted files after a reset, and it has the same chance at recovering the files.
However, if the deleted files are on the system partition, the deleted space may be overwritten during a factory reset. As with any undelete utility, if the deleted file space gets overwritten, the file is unrecoverable.
A factory reset will generally delete the user partition as well as reset the system partition by deleting and overwriting certain files on the system partition.
In general, doing a factory reset will not hinder a file recovery app such as Disk Digger. As long as you want to recover deleted files from the standard partition, a factory reset will not endanger your deleted files any more than continuing to use the device would.