Compilare: user.cpp: In function ‘void solve(int)’: user.cpp:12:10: warning: unused variable ‘c’ [-Wunused-variable] char c=W[i].back(); ^ user.cpp: In function ‘int main()’: user.cpp:29:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.length()) ~^~~~~~~~~~~ user.cpp:37:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<W.size();i++) solve(i); ~^~~~~~~~~