Compilare: main.cpp: In function 'int main()': main.cpp:25:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (n<mystring.size()) ~^~~~~~~~~~~~~~~~ main.cpp:27:19: warning: unused variable 'nr0' [-Wunused-variable] int k=n+7,nr0=0,nr1=0; ^~~ main.cpp:53:12: warning: converting to non-pointer type 'int' from NULL [-Wconversion-null] return NULL; ^~~~