Sol qt4 related package in Ubuntu 18.04

 Problem

E: Unable to locate package qt4-bin-dbg 

E: Package 'qt4-default' has no installation candidate 

E: Package 'qt4-doc' has no installation candidate 

E: Package 'libqt4-dev' has no installation candidate 

E: Unable to locate package libqt4-dev-bin 

Solution

sudo add-apt-repository ppa:rock-core/qt4 

sudo apt install qt4-default 

sudo apt install qt4-bin-dbg 

sudo apt install qt4-doc 

sudo apt install qt4-dev-tools

sudo add-apt-repository --remove ppa:rock-core/qt4