Compilare: user.cpp: In function ‘int main()’: user.cpp:22:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i<s.size(); ++i) ^ user.cpp:26:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=i; j<s.size(); ++j) ^ user.cpp:10:10: warning: unused variable ‘c’ [-Wunused-variable] char c; ^