Compilare: main.cpp: In function 'int main()': main.cpp:17:22: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[sz2] = NULL; ^~~~ main.cpp:24:18: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[sz2] = NULL; ^~~~ main.cpp:35:26: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] aux[k] = NULL; ^~~~ main.cpp:20:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &ok); ^ main.cpp:39:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &ok); ^