Compilare: user.cpp: In function ‘int main()’: user.cpp:42:17: warning: NULL used in arithmetic [-Wpointer-arith] while(s[i]!=NULL){ ^ user.cpp:32:9: warning: unused variable ‘n’ [-Wunused-variable] int n,i=0,m,x,t; ^ user.cpp: In function ‘int pop_S(int, node*, int)’: user.cpp:21:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int pop_D(node*, int)’: user.cpp:28:1: warning: control reaches end of non-void function [-Wreturn-type] } ^