Compilare: user.cpp: In function ‘std::string solve1(std::vector<int>, int)’: user.cpp:14:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); ++i) { ^ user.cpp:17:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < s.size(); ++j) { ^ user.cpp:33:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ^ user.cpp:35:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (ss.str().size() == k) ^ user.cpp: In function ‘int fromstr(std::string)’: user.cpp:47:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ^ user.cpp: In function ‘std::string flip(std::string)’: user.cpp:60:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ^