Compilare: user.cpp: In function ‘void gen(std::string)’: user.cpp:15:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (x.size()==n) a.push_back(x); ^ user.cpp: In function ‘bool sc(std::string, std::string)’: user.cpp:25:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0,j=-1; i<s.size(); i++) ^ user.cpp:28:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=1; j<x.size(); j++) ^ user.cpp:30:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (j==x.size()) return true; ^ user.cpp: In function ‘void ver(std::string)’: user.cpp:37:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:51:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<x.size(); i++) ^ user.cpp:53:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<y.size(); i++) ^