Compilare: main.cpp: In function 'int main()': main.cpp:22:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 22 | for(int i=0; i<line1.length(); i++) { | ~^~~~~~~~~~~~~~~ main.cpp:28:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 28 | for(int j=0; j<line1.length(); j++) { | ~^~~~~~~~~~~~~~~ main.cpp:44:23: warning: array subscript has type 'char' [-Wchar-subscripts] 44 | f[x]++; | ^ main.cpp:46:26: warning: array subscript has type 'char' [-Wchar-subscripts] 46 | if(f[x]==1) { | ^