qt core library

[harshgarg]

can you please share qtcore library.

[amiart]

Please download Qt library from official page:
https://www.qt.io/download

[harshgarg]

which version of qtcore are you using ?? I am getting some errors such as

Also is there any way to use lzstring without using qtcore in cpp

[amiart]

Hi,
The code was tested on Windows (Qt 4.8.7 MSVC2010 32bit, Qt 5.5.1 MSVC2010 32bit, Qt 5.9.4 MSVC2015 32bit) and Linux (Qt 5.5.1 GCC 64bit, Qt 5.9.6 GCC 64bit, Qt 5.11.1 GCC 64bit).

I think the problem lies in the wrong build configuration of your project.
Try google 'Undefined symbols for architecture x86_64' for possible solutions (maybe this?)