Compilare: user.cpp: In function ‘void gen(std::string)’: user.cpp:14:19: 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:24:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0,j=-1; i<s.size(); i++) ^ user.cpp:27:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=1; j<x.size(); j++) ^ user.cpp:29:23: 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:36:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp: In function ‘void bin(std::string)’: user.cpp:44:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (x.size()>=n) ver(x); ^ user.cpp: At global scope: user.cpp:52:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^