Compilare: main.cpp: In function 'int main()': main.cpp:36:37: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sir[k-1][j+1] = NULL; ^~~~ main.cpp:42:38: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sol[lgmax] = NULL; ^~~~ main.cpp:49:29: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sir[k][lgmax] = NULL; ^~~~