Compilare: main.cpp: In function 'void op0(std::string)': main.cpp:26:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 26 | for (int i = 0; i < s.size(); i++) | ~~^~~~~~~~~~ main.cpp: In function 'void op1(std::string)': main.cpp:41:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 41 | for (int i = 0; i < s.size(); i++) | ~~^~~~~~~~~~ main.cpp: In function 'void op2(std::string)': main.cpp:53:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 53 | for (int i = 0; i < s.size(); i++) | ~~^~~~~~~~~~ main.cpp: In function 'void op3(std::string)': main.cpp:70:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 70 | for (i = 0; i < s.size(); i++) | ~~^~~~~~~~~~