Compilare: user.cpp: In function ‘int main()’: user.cpp:16:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0; i < qs[l2 - 1].size(); i++ ) ~~^~~~~~~~~~~~~~~~~~~ user.cpp:18:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int j = 0; j < qs[l2 - 1].size(); j++ ) { ~~^~~~~~~~~~~~~~~~~~~ user.cpp:20:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0; i < qs[l2 - 1].size(); i++ ) ~~^~~~~~~~~~~~~~~~~~~ user.cpp:27:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0; i < qs[num_bits].size(); i++ ) { ~~^~~~~~~~~~~~~~~~~~~~~ user.cpp:11:9: warning: unused variable ‘x’ [-Wunused-variable] int x = 13; ^