Compilare: main.cpp: In function 'int main()': main.cpp:20:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | while(len < s[i-1].size() && len < s[i].size() && s[i-1][len] == s[i][len]){ | ~~~~^~~~~~~~~~~~~~~ main.cpp:20:38: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | while(len < s[i-1].size() && len < s[i].size() && s[i-1][len] == s[i][len]){ | ~~~~^~~~~~~~~~~~~