Compilare: user.cpp: In function ‘int main()’: user.cpp:25:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();++i) a[i]^=s[i]-'0'; ^ user.cpp:28:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();++i) cout<<a[i]; ^