Compilare: user.cpp: In function ‘void prefix(std::string)’: user.cpp:13:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<s.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:29:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<s.size();i++) ^ user.cpp:34:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k==x.size())sol.push_back(i-x.size()+1); ^