Compilare: user.cpp: In function ‘void solve1(std::vector<int>&, int)’: user.cpp:17:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); ++i) { ^ user.cpp:26:36: 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:39:32: 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:52:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ^