How to write this piece separately with a function?

And what's the problem to endure? We look at it - it should not return anything, but Q1 Q2 should be passed as parameters. Total

 void my_func(Queue Q1, Queue Q2) { for (int i=0; i<n; i++) { pr=false; q=(int)Deq(Q1); for (int j=0; j<m; j++) { w=(int)Deq(Q2); if (q==w) pr=true; Enq(Q2,(void*)w); } if (!pr) cout<<q<<endl; Enq(Q1,(void*)q); } for (int i=0; i<m; i++) { pr=false; q=(int)Deq(Q2); for (int j=0; j<n; j++) { w=(int)Deq(Q1); if (q==w) pr=true; Enq(Q1,(void*)w); } if (!pr) cout<<q<<endl; Enq(Q2,(void*)q); } } void main() { int n,q,m,w; bool pr; cin>>n>>m; Queue Q1=CreateQueue(n),Q2=CreateQueue(m); for (int i=0; i<n; i++) {cin>>q; Enq(Q1,(void*)q);} for (int i=0; i<m; i++) {cin>>q; Enq(Q2,(void*)q);} my_func(Q1, Q2); } 

and it's all. Of course, in real code I would write a signature a little differently, for example,

 void my_func(Queue &Q1, Queue &Q2) 

or so

 void my_func(const Queue &Q1, const Queue &Q2) 

these signatures will work for your code.