Compilare: user.cpp: In function ‘std::string prev1(int, std::string)’: user.cpp:24:14: warning: statement has no effect [-Wunused-value] for(i; i<n; ++i) ^ user.cpp: In function ‘std::string next1(int, std::string)’: user.cpp:43:14: warning: statement has no effect [-Wunused-value] for(i; i<n; ++i){ ^ user.cpp:50:20: warning: value computed is not used [-Wunused-value] else s[n-1]=='0'; ^ user.cpp: In function ‘int main()’: user.cpp:72:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=2; i<n; ++i) ^ user.cpp: In function ‘std::string prev1(int, std::string)’: user.cpp:30:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘std::string next1(int, std::string)’: user.cpp:58:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:78:18: warning: ‘c’ may be used uninitialized in this function [-Wmaybe-uninitialized] g<<c%MOD; ^