combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:16:59: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
16 | for(int i=0;i<N-2;i++) k+= (f=p(k+a+k+b+a+k+b+b+k+b+c), f==(k.size()+2)) ? b : (f==(k.size()+1) ? a : c);
| ~^~~~~~~~~~~~~~
combo.cpp:16:83: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
16 | for(int i=0;i<N-2;i++) k+= (f=p(k+a+k+b+a+k+b+b+k+b+c), f==(k.size()+2)) ? b : (f==(k.size()+1) ? a : c);
| ~^~~~~~~~~~~~~~
combo.cpp:17:11: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
17 | if(p(k+a)>(k.size()))k+=a;else if(p(k+b)>(k.size()))k+=b;else k+=c;
| ^
combo.cpp:17:42: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
17 | if(p(k+a)>(k.size()))k+=a;else if(p(k+b)>(k.size()))k+=b;else k+=c;
| ^