Compilare: user.cpp: In function ‘void computepre(std::string)’: user.cpp:23:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < s.size()) { ^ user.cpp: In function ‘int main()’: user.cpp:42:52: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=s1.size(); i < s1.size() + s2.size() + 1; i++) { ^ user.cpp:43:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pre[i] == s1.size()) { ^ user.cpp:53:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < sol.size(); i++) ^