Compilare: main.cpp: In function 'int main()': main.cpp:39:10: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] v[m]=NULL; ^~~~ main.cpp:12:15: warning: unused variable 'j' [-Wunused-variable] int n,m,i,j,sch,x; ^ main.cpp:12:21: warning: unused variable 'x' [-Wunused-variable] int n,m,i,j,sch,x; ^ main.cpp:15:10: warning: unused variable 'a' [-Wunused-variable] char a; ^