Rooting using Windows Application or APK Firstly, I'm so curious about Application one click root, they said in their homepage, they can root with just one click within single Apps. For Samsung Devices which we know cannot using fastboot through ADB (bootloader locked), so we need to install custom recovery through Odin/Heimdall. (for beginner is such a confused things). 

So, how they can rooting any devices without Odin/Heimdall and CWM/TWRP custom recovery?

And after several doing research on internet, I've found that some Android Application have ability to rooting device. I know rooting devices doesn't need to install custom recovery. 

how APK can root devices without gain root access? How it can be done? and can you refer some application code or snippet code that purposed to root devices? 

Any help would be appreciated. Thanks.
Some devices need that thing(custom recovery/pre-root) to "set the road" to the root application. Take in mind that rooting a device is exploiting a system bug to gain root access.

Because of that I don't think that would be possible for an app to root the device just for one app. It's the entire device what is rooted, not just an app.