K Reverse LL problem

#1

can not understand the line 65

#2

Hey Assume
we have
linked list 1 2 3 4
and k=2
So
after reversing first 2 nodes
2->1 but head still points to 1
so we have to connect the remaining linked list after reversing to head->next
So here we call 1->next=reverse( 3->4,2)
so we reverse 4->3 and set 3->next=NULL; and return 4
so 1->next connects to 4
and we return 2